I'm solving for a derivative, which is no prob, but I don't remember all the trig rules. So leaving out the calculus the equation boils down to:

$\displaystyle f\prime(x)=\cos(\frac{\pi}{4})-(\frac{\pi}{4})\sin(\frac{\pi}{4})$

Which i can just plug in to my calculator and get a numerical answer but they want it factored into

$\displaystyle f\prime(x)=\frac{\sqrt{2}}{8}(4-\pi)$

Would someone mind showing me the steps again? I need to review my trig (Wondering)