let X, Y be RealNormSpace; :: thesis: for f being bounded LinearOperator of X,Y holds (BoundedLinearOperatorsNorm (X,Y)) . f = upper_bound (PreNorms f)
let f be bounded LinearOperator of X,Y; :: thesis: (BoundedLinearOperatorsNorm (X,Y)) . f = upper_bound (PreNorms f)
reconsider f9 = f as set ;
f in BoundedLinearOperators (X,Y) by Def10;
hence (BoundedLinearOperatorsNorm (X,Y)) . f = upper_bound (PreNorms (modetrans (f9,X,Y))) by Def14
.= upper_bound (PreNorms f) by Th35 ;
:: thesis: verum