If f(x) (pi-x) sec2(x) then f'(pi4)?

Answer 1

If that is a product, (pi-x) times (sec squared x), then you can use the product rule for derivatives. For the power, sec squared x, which simply means (sec x) squared, you can use the chain rule.

Answer 2

The browser used for posting questions on this site is rubbish. It is quite useless for mathematics since it strips out most symbols so that we cannot tell what the question is meant to be.

If f(x) = (pi - x)*sec2x

then f'(x) = (pi - x)*2*sec2x*tan(x) - sec2x

Then, if it is f'(pi/4) that you require, the answer is 3*pi/4 - 1/2.