Thread: Partial Derivative

hi everyone,

im trying to do the partial derivate of x^tAx ..please could you see the image? it will make more sense

what i dont know is how they got the partial derivative. and why is it 2a(ii). how did it change to a(ii) from a(ij)

i hope it's clear and Thank you very much everyone

Originally Posted by matlabnoob

hi everyone,

im trying to do the partial derivate of x^tAx ..please could you see the image? it will make more sense

what i dont know is how they got the partial derivative. and why is it 2a(ii). how did it change to a(ii) from a(ij)

Are you aware the are the diagnal elements of A?

Also is a quadratic form.

Originally Posted by pickslides

Are you aware the are the diagnal elements of A?

Also is a quadratic form.

i am aware of this, but still do not understand how the partial derivative is done. i thought all you do is ignore the other terms, look at x(i) so you get the sum of a(ij)*x(i) ? but this is not the case here?