its been a while...but im back. i've been working really hard and finally have another question.
is cos(θ+π2=−sin(θ) a true identity?
Here is a graph of cos (x + pi/2):
and here is a graph of - sin x :
WHat do you think?
We can use the angle sum identitiy for the cosine to check this ........
cos (θ + π/2) =
cos θ cos π/2 - sin θ sin π/2 =
cos θ * ( 0 ) - sin θ * (1) =
-sin θ
So...this is an identity !!!
+577 
+37165 
