Trig and Radians Confusion I am learning about radians in my current class and am totally confused.
How does $\sin(x+\frac\pi 2)=\cos(x)$ when $\frac\pi 2<x$ < $\pi$.
I drew the triangles and I got
$\sin(x+\frac\pi 2)=\frac{-\mathrm{opposite}}{-\mathrm{hypotenuse}}=\frac{\mathrm{opp}}{\mathrm{hyp}}$
$\cos(x)=\frac{\mathrm{adjacent}}{\mathrm{hypotenuse}}$
If the adjacent equals the hypotenuse this should work however in most circumstances this isn't true.  What is the major flaw in my work??
Here is what I drew out.


It's just how it is, if you look at a graph of sine and overlay cosine on top of it, then this would be readily apparent. 
