# My simple trig is rusty..

• Feb 8th 2009, 07:31 AM
ixo
My simple trig is rusty..
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:
$f\prime(x)=\cos(\frac{\pi}{4})-(\frac{\pi}{4})\sin(\frac{\pi}{4})$

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

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

Would someone mind showing me the steps again? I need to review my trig (Wondering)
• Feb 8th 2009, 07:38 AM
running-gag
Hi

$\cos \left(\frac{\pi}{4}\right) = \sin \left(\frac{\pi}{4}\right) = \frac{\sqrt{2}}{2}$
• Feb 8th 2009, 07:52 AM
ixo
trig common angles.. lol thx i was trying to open them up.