P. 122 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 12101-12200   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	rexmul 12101	The extended real multiplication when both arguments are real. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR /\ B e. RR ) -> ( A xe B ) = ( A x. B ) )
Theorem	xmulf 12102	The extended real multiplication operation is closed in extended reals. (Contributed by Mario Carneiro, 21-Aug-2015.)
|- xe : ( RR* X. RR* ) --> RR*
Theorem	xmulcl 12103	Closure of extended real multiplication. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* ) -> ( A xe B ) e. RR* )
Theorem	xmulpnf1 12104	Multiplication by plus infinity on the right. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ 0 < A ) -> ( A xe +oo ) = +oo )
Theorem	xmulpnf2 12105	Multiplication by plus infinity on the left. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ 0 < A ) -> ( +oo xe A ) = +oo )
Theorem	xmulmnf1 12106	Multiplication by minus infinity on the right. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ 0 < A ) -> ( A xe -oo ) = -oo )
Theorem	xmulmnf2 12107	Multiplication by minus infinity on the left. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ 0 < A ) -> ( -oo xe A ) = -oo )
Theorem	xmulpnf1n 12108	Multiplication by plus infinity on the right, for negative input. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ A < 0 ) -> ( A xe +oo ) = -oo )
Theorem	xmulid1 12109	Extended real version of mulid1 10037. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( A e. RR* -> ( A xe 1 ) = A )
Theorem	xmulid2 12110	Extended real version of mulid2 10038. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( A e. RR* -> ( 1 xe A ) = A )
Theorem	xmulm1 12111	Extended real version of mulm1 10471. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( A e. RR* -> ( -u 1 xe A ) = -e A )
Theorem	xmulasslem2 12112	Lemma for xmulass 12117. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( 0 < A /\ A = -oo ) -> ph )
Theorem	xmulgt0 12113	Extended real version of mulgt0 10115. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR* /\ 0 < A ) /\ ( B e. RR* /\ 0 < B ) ) -> 0 < ( A xe B ) )
Theorem	xmulge0 12114	Extended real version of mulge0 10546. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR* /\ 0 <_ A ) /\ ( B e. RR* /\ 0 <_ B ) ) -> 0 <_ ( A xe B ) )
Theorem	xmulasslem 12115*	Lemma for xmulass 12117. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( x = D -> ( ps <-> X = Y ) )   &    |- ( x = -e D -> ( ps <-> E = F ) )   &    |- ( ph -> X e. RR* )   &    |- ( ph -> Y e. RR* )   &    |- ( ph -> D e. RR* )   &    |- ( ( ph /\ ( x e. RR* /\ 0 < x ) ) -> ps )   &    |- ( ph -> ( x = 0 -> ps ) )   &    |- ( ph -> E = -e X )   &    |- ( ph -> F = -e Y )   =>    |- ( ph -> X = Y )
Theorem	xmulasslem3 12116	Lemma for xmulass 12117. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR* /\ 0 < A ) /\ ( B e. RR* /\ 0 < B ) /\ ( C e. RR* /\ 0 < C ) ) -> ( ( A xe B ) xe C ) = ( A xe ( B xe C ) ) )
Theorem	xmulass 12117	Associativity of the extended real multiplication operation. Surprisingly, there are no restrictions on the values, unlike xaddass 12079 which has to avoid the "undefined" combinations +oo +e -oo and -oo +e +oo. The equivalent "undefined" expression here would be 0 xe +oo, but since this is defined to equal 0 any zeroes in the expression make the whole thing evaluate to zero (on both sides), thus establishing the identity in this case. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR* ) -> ( ( A xe B ) xe C ) = ( A xe ( B xe C ) ) )
Theorem	xlemul1a 12118	Extended real version of lemul1a 10877. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR* /\ B e. RR* /\ ( C e. RR* /\ 0 <_ C ) ) /\ A <_ B ) -> ( A xe C ) <_ ( B xe C ) )
Theorem	xlemul2a 12119	Extended real version of lemul2a 10878. (Contributed by Mario Carneiro, 8-Sep-2015.)
|- ( ( ( A e. RR* /\ B e. RR* /\ ( C e. RR* /\ 0 <_ C ) ) /\ A <_ B ) -> ( C xe A ) <_ ( C xe B ) )
Theorem	xlemul1 12120	Extended real version of lemul1 10875. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR+ ) -> ( A <_ B <-> ( A xe C ) <_ ( B xe C ) ) )
Theorem	xlemul2 12121	Extended real version of lemul2 10876. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR+ ) -> ( A <_ B <-> ( C xe A ) <_ ( C xe B ) ) )
Theorem	xltmul1 12122	Extended real version of ltmul1 10873. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR+ ) -> ( A < B <-> ( A xe C ) < ( B xe C ) ) )
Theorem	xltmul2 12123	Extended real version of ltmul2 10874. (Contributed by Mario Carneiro, 8-Sep-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR+ ) -> ( A < B <-> ( C xe A ) < ( C xe B ) ) )
Theorem	xadddilem 12124	Lemma for xadddi 12125. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR /\ B e. RR* /\ C e. RR* ) /\ 0 < A ) -> ( A xe ( B +e C ) ) = ( ( A xe B ) +e ( A xe C ) ) )
Theorem	xadddi 12125	Distributive property for extended real addition and multiplication. Like xaddass 12079, this has an unusual domain of correctness due to counterexamples like ( +oo x. ( 2 - 1 ) ) = -oo =/= ( ( +oo x. 2 ) - ( +oo x. 1 ) ) = ( +oo - +oo ) = 0. In this theorem we show that if the multiplier is real then everything works as expected. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR /\ B e. RR* /\ C e. RR* ) -> ( A xe ( B +e C ) ) = ( ( A xe B ) +e ( A xe C ) ) )
Theorem	xadddir 12126	Commuted version of xadddi 12125. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ B e. RR* /\ C e. RR ) -> ( ( A +e B ) xe C ) = ( ( A xe C ) +e ( B xe C ) ) )
Theorem	xadddi2 12127	The assumption that the multiplier be real in xadddi 12125 can be relaxed if the addends have the same sign. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( A e. RR* /\ ( B e. RR* /\ 0 <_ B ) /\ ( C e. RR* /\ 0 <_ C ) ) -> ( A xe ( B +e C ) ) = ( ( A xe B ) +e ( A xe C ) ) )
Theorem	xadddi2r 12128	Commuted version of xadddi2 12127. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( ( ( A e. RR* /\ 0 <_ A ) /\ ( B e. RR* /\ 0 <_ B ) /\ C e. RR* ) -> ( ( A +e B ) xe C ) = ( ( A xe C ) +e ( B xe C ) ) )
Theorem	x2times 12129	Extended real version of 2times 11145. (Contributed by Mario Carneiro, 20-Aug-2015.)
|- ( A e. RR* -> ( 2 xe A ) = ( A +e A ) )
Theorem	xnegcld 12130	Closure of extended real negative. (Contributed by Mario Carneiro, 28-May-2016.)
|- ( ph -> A e. RR* )   =>    |- ( ph -> -e A e. RR* )
Theorem	xaddcld 12131	The extended real addition operation is closed in extended reals. (Contributed by Mario Carneiro, 28-May-2016.)
|- ( ph -> A e. RR* )   &    |- ( ph -> B e. RR* )   =>    |- ( ph -> ( A +e B ) e. RR* )
Theorem	xmulcld 12132	Closure of extended real multiplication. (Contributed by Mario Carneiro, 28-May-2016.)
|- ( ph -> A e. RR* )   &    |- ( ph -> B e. RR* )   =>    |- ( ph -> ( A xe B ) e. RR* )
Theorem	xadd4d 12133	Rearrangement of 4 terms in a sum for extended addition, analogous to add4d 10264. (Contributed by Alexander van der Vekens, 21-Dec-2017.)
|- ( ph -> ( A e. RR* /\ A =/= -oo ) )   &    |- ( ph -> ( B e. RR* /\ B =/= -oo ) )   &    |- ( ph -> ( C e. RR* /\ C =/= -oo ) )   &    |- ( ph -> ( D e. RR* /\ D =/= -oo ) )   =>    |- ( ph -> ( ( A +e B ) +e ( C +e D ) ) = ( ( A +e C ) +e ( B +e D ) ) )
Theorem	xnn0add4d 12134	Rearrangement of 4 terms in a sum for extended addition of extended nonnegative integers, analogous to xadd4d 12133. (Contributed by AV, 12-Dec-2020.)
|- ( ph -> A e. NN0* )   &    |- ( ph -> B e. NN0* )   &    |- ( ph -> C e. NN0* )   &    |- ( ph -> D e. NN0* )   =>    |- ( ph -> ( ( A +e B ) +e ( C +e D ) ) = ( ( A +e C ) +e ( B +e D ) ) )
5.5.3  Supremum and infimum on the extended reals
Theorem	xrsupexmnf 12135*	Adding minus infinity to a set does not affect the existence of its supremum. (Contributed by NM, 26-Oct-2005.)
|- ( E. x e. RR* ( A. y e. A -. x < y /\ A. y e. RR* ( y < x -> E. z e. A y < z ) ) -> E. x e. RR* ( A. y e. ( A u. { -oo } ) -. x < y /\ A. y e. RR* ( y < x -> E. z e. ( A u. { -oo } ) y < z ) ) )
Theorem	xrinfmexpnf 12136*	Adding plus infinity to a set does not affect the existence of its infimum. (Contributed by NM, 19-Jan-2006.)
|- ( E. x e. RR* ( A. y e. A -. y < x /\ A. y e. RR* ( x < y -> E. z e. A z < y ) ) -> E. x e. RR* ( A. y e. ( A u. { +oo } ) -. y < x /\ A. y e. RR* ( x < y -> E. z e. ( A u. { +oo } ) z < y ) ) )
Theorem	xrsupsslem 12137*	Lemma for xrsupss 12139. (Contributed by NM, 25-Oct-2005.)
|- ( ( A C_ RR* /\ ( A C_ RR \/ +oo e. A ) ) -> E. x e. RR* ( A. y e. A -. x < y /\ A. y e. RR* ( y < x -> E. z e. A y < z ) ) )
Theorem	xrinfmsslem 12138*	Lemma for xrinfmss 12140. (Contributed by NM, 19-Jan-2006.)
|- ( ( A C_ RR* /\ ( A C_ RR \/ -oo e. A ) ) -> E. x e. RR* ( A. y e. A -. y < x /\ A. y e. RR* ( x < y -> E. z e. A z < y ) ) )
Theorem	xrsupss 12139*	Any subset of extended reals has a supremum. (Contributed by NM, 25-Oct-2005.)
|- ( A C_ RR* -> E. x e. RR* ( A. y e. A -. x < y /\ A. y e. RR* ( y < x -> E. z e. A y < z ) ) )
Theorem	xrinfmss 12140*	Any subset of extended reals has an infimum. (Contributed by NM, 25-Oct-2005.)
|- ( A C_ RR* -> E. x e. RR* ( A. y e. A -. y < x /\ A. y e. RR* ( x < y -> E. z e. A z < y ) ) )
Theorem	xrinfmss2 12141*	Any subset of extended reals has an infimum. (Contributed by Mario Carneiro, 16-Mar-2014.)
|- ( A C_ RR* -> E. x e. RR* ( A. y e. A -. x `' < y /\ A. y e. RR* ( y `' < x -> E. z e. A y `' < z ) ) )
Theorem	xrub 12142*	By quantifying only over reals, we can specify any extended real upper bound for any set of extended reals. (Contributed by NM, 9-Apr-2006.)
|- ( ( A C_ RR* /\ B e. RR* ) -> ( A. x e. RR ( x < B -> E. y e. A x < y ) <-> A. x e. RR* ( x < B -> E. y e. A x < y ) ) )
Theorem	supxr 12143*	The supremum of a set of extended reals. (Contributed by NM, 9-Apr-2006.) (Revised by Mario Carneiro, 21-Apr-2015.)
|- ( ( ( A C_ RR* /\ B e. RR* ) /\ ( A. x e. A -. B < x /\ A. x e. RR ( x < B -> E. y e. A x < y ) ) ) -> sup ( A , RR* , < ) = B )
Theorem	supxr2 12144*	The supremum of a set of extended reals. (Contributed by NM, 9-Apr-2006.)
|- ( ( ( A C_ RR* /\ B e. RR* ) /\ ( A. x e. A x <_ B /\ A. x e. RR ( x < B -> E. y e. A x < y ) ) ) -> sup ( A , RR* , < ) = B )
Theorem	supxrcl 12145	The supremum of an arbitrary set of extended reals is an extended real. (Contributed by NM, 24-Oct-2005.)
|- ( A C_ RR* -> sup ( A , RR* , < ) e. RR* )
Theorem	supxrun 12146	The supremum of the union of two sets of extended reals equals the largest of their suprema. (Contributed by NM, 19-Jan-2006.)
|- ( ( A C_ RR* /\ B C_ RR* /\ sup ( A , RR* , < ) <_ sup ( B , RR* , < ) ) -> sup ( ( A u. B ) , RR* , < ) = sup ( B , RR* , < ) )
Theorem	supxrmnf 12147	Adding minus infinity to a set does not affect its supremum. (Contributed by NM, 19-Jan-2006.)
|- ( A C_ RR* -> sup ( ( A u. { -oo } ) , RR* , < ) = sup ( A , RR* , < ) )
Theorem	supxrpnf 12148	The supremum of a set of extended reals containing plus infinity is plus infinity. (Contributed by NM, 15-Oct-2005.)
|- ( ( A C_ RR* /\ +oo e. A ) -> sup ( A , RR* , < ) = +oo )
Theorem	supxrunb1 12149*	The supremum of an unbounded-above set of extended reals is plus infinity. (Contributed by NM, 19-Jan-2006.)
|- ( A C_ RR* -> ( A. x e. RR E. y e. A x <_ y <-> sup ( A , RR* , < ) = +oo ) )
Theorem	supxrunb2 12150*	The supremum of an unbounded-above set of extended reals is plus infinity. (Contributed by NM, 19-Jan-2006.)
|- ( A C_ RR* -> ( A. x e. RR E. y e. A x < y <-> sup ( A , RR* , < ) = +oo ) )
Theorem	supxrbnd1 12151*	The supremum of a bounded-above set of extended reals is less than infinity. (Contributed by NM, 30-Jan-2006.)
|- ( A C_ RR* -> ( E. x e. RR A. y e. A y < x <-> sup ( A , RR* , < ) < +oo ) )
Theorem	supxrbnd2 12152*	The supremum of a bounded-above set of extended reals is less than infinity. (Contributed by NM, 30-Jan-2006.)
|- ( A C_ RR* -> ( E. x e. RR A. y e. A y <_ x <-> sup ( A , RR* , < ) < +oo ) )
Theorem	xrsup0 12153	The supremum of an empty set under the extended reals is minus infinity. (Contributed by NM, 15-Oct-2005.)
|- sup ( (/) , RR* , < ) = -oo
Theorem	supxrub 12154	A member of a set of extended reals is less than or equal to the set's supremum. (Contributed by NM, 7-Feb-2006.)
|- ( ( A C_ RR* /\ B e. A ) -> B <_ sup ( A , RR* , < ) )
Theorem	supxrlub 12155*	The supremum of a set of extended reals is less than or equal to an upper bound. (Contributed by Mario Carneiro, 13-Sep-2015.)
|- ( ( A C_ RR* /\ B e. RR* ) -> ( B < sup ( A , RR* , < ) <-> E. x e. A B < x ) )
Theorem	supxrleub 12156*	The supremum of a set of extended reals is less than or equal to an upper bound. (Contributed by NM, 22-Feb-2006.) (Revised by Mario Carneiro, 6-Sep-2014.)
|- ( ( A C_ RR* /\ B e. RR* ) -> ( sup ( A , RR* , < ) <_ B <-> A. x e. A x <_ B ) )
Theorem	supxrre 12157*	The real and extended real suprema match when the real supremum exists. (Contributed by NM, 18-Oct-2005.) (Proof shortened by Mario Carneiro, 7-Sep-2014.)
|- ( ( A C_ RR /\ A =/= (/) /\ E. x e. RR A. y e. A y <_ x ) -> sup ( A , RR* , < ) = sup ( A , RR , < ) )
Theorem	supxrbnd 12158	The supremum of a bounded-above nonempty set of reals is real. (Contributed by NM, 19-Jan-2006.)
|- ( ( A C_ RR /\ A =/= (/) /\ sup ( A , RR* , < ) < +oo ) -> sup ( A , RR* , < ) e. RR )
Theorem	supxrgtmnf 12159	The supremum of a nonempty set of reals is greater than minus infinity. (Contributed by NM, 2-Feb-2006.)
|- ( ( A C_ RR /\ A =/= (/) ) -> -oo < sup ( A , RR* , < ) )
Theorem	supxrre1 12160	The supremum of a nonempty set of reals is real iff it is less than plus infinity. (Contributed by NM, 5-Feb-2006.)
|- ( ( A C_ RR /\ A =/= (/) ) -> ( sup ( A , RR* , < ) e. RR <-> sup ( A , RR* , < ) < +oo ) )
Theorem	supxrre2 12161	The supremum of a nonempty set of reals is real iff it is not plus infinity. (Contributed by NM, 5-Feb-2006.)
|- ( ( A C_ RR /\ A =/= (/) ) -> ( sup ( A , RR* , < ) e. RR <-> sup ( A , RR* , < ) =/= +oo ) )
Theorem	supxrss 12162	Smaller sets of extended reals have smaller suprema. (Contributed by Mario Carneiro, 1-Apr-2015.)
|- ( ( A C_ B /\ B C_ RR* ) -> sup ( A , RR* , < ) <_ sup ( B , RR* , < ) )
Theorem	infxrcl 12163	The infimum of an arbitrary set of extended reals is an extended real. (Contributed by NM, 19-Jan-2006.) (Revised by AV, 5-Sep-2020.)
|- ( A C_ RR* -> inf ( A , RR* , < ) e. RR* )
Theorem	infxrlb 12164	A member of a set of extended reals is greater than or equal to the set's infimum. (Contributed by Mario Carneiro, 16-Mar-2014.) (Revised by AV, 5-Sep-2020.)
|- ( ( A C_ RR* /\ B e. A ) -> inf ( A , RR* , < ) <_ B )
Theorem	infxrgelb 12165*	The infimum of a set of extended reals is greater than or equal to a lower bound. (Contributed by Mario Carneiro, 16-Mar-2014.) (Revised by AV, 5-Sep-2020.)
|- ( ( A C_ RR* /\ B e. RR* ) -> ( B <_ inf ( A , RR* , < ) <-> A. x e. A B <_ x ) )
Theorem	infxrre 12166*	The real and extended real infima match when the real infimum exists. (Contributed by Mario Carneiro, 7-Sep-2014.) (Revised by AV, 5-Sep-2020.)
|- ( ( A C_ RR /\ A =/= (/) /\ E. x e. RR A. y e. A x <_ y ) -> inf ( A , RR* , < ) = inf ( A , RR , < ) )
Theorem	infxrmnf 12167	The infinimum of a set of extended reals containing minus infinity is minus infinity. (Contributed by Thierry Arnoux, 18-Feb-2018.) (Revised by AV, 28-Sep-2020.)
|- ( ( A C_ RR* /\ -oo e. A ) -> inf ( A , RR* , < ) = -oo )
Theorem	xrinf0 12168	The infimum of the empty set under the extended reals is positive infinity. (Contributed by Mario Carneiro, 21-Apr-2015.) (Revised by AV, 5-Sep-2020.)
|- inf ( (/) , RR* , < ) = +oo
Theorem	infxrss 12169	Larger sets of extended reals have smaller infima. (Contributed by Glauco Siliprandi, 11-Dec-2019.) (Revised by AV, 13-Sep-2020.)
|- ( ( A C_ B /\ B C_ RR* ) -> inf ( B , RR* , < ) <_ inf ( A , RR* , < ) )
Theorem	reltre 12170*	For all real numbers there is a smaller real number. (Contributed by AV, 5-Sep-2020.)
|- A. x e. RR E. y e. RR y < x
Theorem	rpltrp 12171*	For all positive real numbers there is a smaller positive real number. (Contributed by AV, 5-Sep-2020.)
|- A. x e. RR+ E. y e. RR+ y < x
Theorem	reltxrnmnf 12172*	For all extended real numbers not being minus infinity there is a smaller real number. (Contributed by AV, 5-Sep-2020.)
|- A. x e. RR* ( -oo < x -> E. y e. RR y < x )
Theorem	infmremnf 12173	The infimum of the reals is minus infinity. (Contributed by AV, 5-Sep-2020.)
|- inf ( RR , RR* , < ) = -oo
Theorem	infmrp1 12174	The infimum of the positive reals is 0. (Contributed by AV, 5-Sep-2020.)
|- inf ( RR+ , RR , < ) = 0
5.5.4  Real number intervals
Syntax	cioo 12175	Extend class notation with the set of open intervals of extended reals.
class (,)
Syntax	cioc 12176	Extend class notation with the set of open-below, closed-above intervals of extended reals.
class (,]
Syntax	cico 12177	Extend class notation with the set of closed-below, open-above intervals of extended reals.
class [,)
Syntax	cicc 12178	Extend class notation with the set of closed intervals of extended reals.
class [,]
Definition	df-ioo 12179*	Define the set of open intervals of extended reals. (Contributed by NM, 24-Dec-2006.)
|- (,) = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x < z /\ z < y ) } )
Definition	df-ioc 12180*	Define the set of open-below, closed-above intervals of extended reals. (Contributed by NM, 24-Dec-2006.)
|- (,] = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x < z /\ z <_ y ) } )
Definition	df-ico 12181*	Define the set of closed-below, open-above intervals of extended reals. (Contributed by NM, 24-Dec-2006.)
|- [,) = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x <_ z /\ z < y ) } )
Definition	df-icc 12182*	Define the set of closed intervals of extended reals. (Contributed by NM, 24-Dec-2006.)
|- [,] = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x <_ z /\ z <_ y ) } )
Theorem	ixxval 12183*	Value of the interval function. (Contributed by Mario Carneiro, 3-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- ( ( A e. RR* /\ B e. RR* ) -> ( A O B ) = { z e. RR* | ( A R z /\ z S B ) } )
Theorem	elixx1 12184*	Membership in an interval of extended reals. (Contributed by Mario Carneiro, 3-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- ( ( A e. RR* /\ B e. RR* ) -> ( C e. ( A O B ) <-> ( C e. RR* /\ A R C /\ C S B ) ) )
Theorem	ixxf 12185*	The set of intervals of extended reals maps to subsets of extended reals. (Contributed by FL, 14-Jun-2007.) (Revised by Mario Carneiro, 16-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- O : ( RR* X. RR* ) --> ~P RR*
Theorem	ixxex 12186*	The set of intervals of extended reals exists. (Contributed by Mario Carneiro, 3-Nov-2013.) (Revised by Mario Carneiro, 17-Nov-2014.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- O e. _V
Theorem	ixxssxr 12187*	The set of intervals of extended reals maps to subsets of extended reals. (Contributed by Mario Carneiro, 4-Jul-2014.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- ( A O B ) C_ RR*
Theorem	elixx3g 12188*	Membership in a set of open intervals of extended reals. We use the fact that an operation's value is empty outside of its domain to show A e. RR* and B e. RR*. (Contributed by Mario Carneiro, 3-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   =>    |- ( C e. ( A O B ) <-> ( ( A e. RR* /\ B e. RR* /\ C e. RR* ) /\ ( A R C /\ C S B ) ) )
Theorem	ixxssixx 12189*	An interval is a subset of its closure. (Contributed by Paul Chapman, 18-Oct-2007.) (Revised by Mario Carneiro, 3-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x T z /\ z U y ) } )   &    |- ( ( A e. RR* /\ w e. RR* ) -> ( A R w -> A T w ) )   &    |- ( ( w e. RR* /\ B e. RR* ) -> ( w S B -> w U B ) )   =>    |- ( A O B ) C_ ( A P B )
Theorem	ixxdisj 12190*	Split an interval into disjoint pieces. (Contributed by Mario Carneiro, 16-Jun-2014.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x T z /\ z U y ) } )   &    |- ( ( B e. RR* /\ w e. RR* ) -> ( B T w <-> -. w S B ) )   =>    |- ( ( A e. RR* /\ B e. RR* /\ C e. RR* ) -> ( ( A O B ) i^i ( B P C ) ) = (/) )
Theorem	ixxun 12191*	Split an interval into two parts. (Contributed by Mario Carneiro, 16-Jun-2014.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x T z /\ z U y ) } )   &    |- ( ( B e. RR* /\ w e. RR* ) -> ( B T w <-> -. w S B ) )   &    |- Q = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z U y ) } )   &    |- ( ( w e. RR* /\ B e. RR* /\ C e. RR* ) -> ( ( w S B /\ B X C ) -> w U C ) )   &    |- ( ( A e. RR* /\ B e. RR* /\ w e. RR* ) -> ( ( A W B /\ B T w ) -> A R w ) )   =>    |- ( ( ( A e. RR* /\ B e. RR* /\ C e. RR* ) /\ ( A W B /\ B X C ) ) -> ( ( A O B ) u. ( B P C ) ) = ( A Q C ) )
Theorem	ixxin 12192*	Intersection of two intervals of extended reals. (Contributed by Mario Carneiro, 3-Nov-2013.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- ( ( A e. RR* /\ C e. RR* /\ z e. RR* ) -> ( if ( A <_ C , C , A ) R z <-> ( A R z /\ C R z ) ) )   &    |- ( ( z e. RR* /\ B e. RR* /\ D e. RR* ) -> ( z S if ( B <_ D , B , D ) <-> ( z S B /\ z S D ) ) )   =>    |- ( ( ( A e. RR* /\ B e. RR* ) /\ ( C e. RR* /\ D e. RR* ) ) -> ( ( A O B ) i^i ( C O D ) ) = ( if ( A <_ C , C , A ) O if ( B <_ D , B , D ) ) )
Theorem	ixxss1 12193*	Subset relationship for intervals of extended reals. (Contributed by Mario Carneiro, 3-Nov-2013.) (Revised by Mario Carneiro, 28-Apr-2015.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x T z /\ z S y ) } )   &    |- ( ( A e. RR* /\ B e. RR* /\ w e. RR* ) -> ( ( A W B /\ B T w ) -> A R w ) )   =>    |- ( ( A e. RR* /\ A W B ) -> ( B P C ) C_ ( A O C ) )
Theorem	ixxss2 12194*	Subset relationship for intervals of extended reals. (Contributed by Mario Carneiro, 3-Nov-2013.) (Revised by Mario Carneiro, 28-Apr-2015.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z T y ) } )   &    |- ( ( w e. RR* /\ B e. RR* /\ C e. RR* ) -> ( ( w T B /\ B W C ) -> w S C ) )   =>    |- ( ( C e. RR* /\ B W C ) -> ( A P B ) C_ ( A O C ) )
Theorem	ixxss12 12195*	Subset relationship for intervals of extended reals. (Contributed by Mario Carneiro, 20-Feb-2015.) (Revised by Mario Carneiro, 28-Apr-2015.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- P = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x T z /\ z U y ) } )   &    |- ( ( A e. RR* /\ C e. RR* /\ w e. RR* ) -> ( ( A W C /\ C T w ) -> A R w ) )   &    |- ( ( w e. RR* /\ D e. RR* /\ B e. RR* ) -> ( ( w U D /\ D X B ) -> w S B ) )   =>    |- ( ( ( A e. RR* /\ B e. RR* ) /\ ( A W C /\ D X B ) ) -> ( C P D ) C_ ( A O B ) )
Theorem	ixxub 12196*	Extract the upper bound of an interval. (Contributed by Mario Carneiro, 17-Jun-2014.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- ( ( w e. RR* /\ B e. RR* ) -> ( w < B -> w S B ) )   &    |- ( ( w e. RR* /\ B e. RR* ) -> ( w S B -> w <_ B ) )   &    |- ( ( A e. RR* /\ w e. RR* ) -> ( A < w -> A R w ) )   &    |- ( ( A e. RR* /\ w e. RR* ) -> ( A R w -> A <_ w ) )   =>    |- ( ( A e. RR* /\ B e. RR* /\ ( A O B ) =/= (/) ) -> sup ( ( A O B ) , RR* , < ) = B )
Theorem	ixxlb 12197*	Extract the lower bound of an interval. (Contributed by Mario Carneiro, 17-Jun-2014.) (Revised by AV, 12-Sep-2020.)
|- O = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x R z /\ z S y ) } )   &    |- ( ( w e. RR* /\ B e. RR* ) -> ( w < B -> w S B ) )   &    |- ( ( w e. RR* /\ B e. RR* ) -> ( w S B -> w <_ B ) )   &    |- ( ( A e. RR* /\ w e. RR* ) -> ( A < w -> A R w ) )   &    |- ( ( A e. RR* /\ w e. RR* ) -> ( A R w -> A <_ w ) )   =>    |- ( ( A e. RR* /\ B e. RR* /\ ( A O B ) =/= (/) ) -> inf ( ( A O B ) , RR* , < ) = A )
Theorem	iooex 12198	The set of open intervals of extended reals exists. (Contributed by NM, 6-Feb-2007.) (Revised by Mario Carneiro, 3-Nov-2013.)
|- (,) e. _V
Theorem	iooval 12199*	Value of the open interval function. (Contributed by NM, 24-Dec-2006.) (Revised by Mario Carneiro, 3-Nov-2013.)
|- ( ( A e. RR* /\ B e. RR* ) -> ( A (,) B ) = { x e. RR* | ( A < x /\ x < B ) } )
Theorem	ioo0 12200	An empty open interval of extended reals. (Contributed by NM, 6-Feb-2007.)
|- ( ( A e. RR* /\ B e. RR* ) -> ( ( A (,) B ) = (/) <-> B <_ A ) )