let x, y be FinSequence of COMPLEX ; for M being Matrix of COMPLEX st len x = width M & len y = len M & width M > 0 & len M > 0 holds
|((M * x),y)| = |(x,((M @" ) * y))|
let M be Matrix of COMPLEX ; ( len x = width M & len y = len M & width M > 0 & len M > 0 implies |((M * x),y)| = |(x,((M @" ) * y))| )
assume that
A1:
len x = width M
and
A2:
len y = len M
and
A3:
width M > 0
and
A4:
len M > 0
; |((M * x),y)| = |(x,((M @" ) * y))|
|(x,((M @" ) * y))| = SumAll (QuadraticForm x,(M @ ),y)
by A1, A2, A3, A4, Th60;
hence
|((M * x),y)| = |(x,((M @" ) * y))|
by A1, A2, A3, A4, Th61; verum