16.-Linear-Algebra-by-Kenneth-Hoffman · Problem 10.4.12
Bilinear Forms
Mathematics — Linear Algebra · matrix-preserving-bilinear-form
Problem
Let F be a subfield of C, V the space of n×1 matrices over F, A an invertible n×n matrix over F, and f the bilinear form on V given by f(X,Y)=XtAY. If M is an n×n matrix over F, show that M preserves f if and only if A−1MtA=M−1.