1
$\begingroup$

The following is given for $ ∂x^TAx/∂x $ in a book on Matrix Algebra: ∂xTAx/∂x

What I cannot understand is: Where does $A^T$ come from in the second row (in the term $ ty^TA^Tx $)?

$\endgroup$
0
$\begingroup$

Since $a=a^T$ for a scalar value $a$, $$tx^TAy=t(x^TAy)^T=ty^TA^Tx$$

$\endgroup$
1
  • $\begingroup$ Very helpful, thank you! So one important bit when doing these sort of manipulations seems to be to be constantly aware of what the outcome of operations are (scalar, vector, or matrix). If anyone had a pointer to exercises doing this sort of stuff, it'ld be very helpful. I'll also look around myself. Thanks again $\endgroup$ – SpiderMonkey Dec 14 '14 at 15:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.