# Identity

• May 2nd 2010, 12:27 PM
Hellooo
Identity
Prove that, sin2x+sin2y=2sin(x+y)cos(x-y).

• May 2nd 2010, 05:53 PM
sa-ri-ga-ma
Quote:

Originally Posted by Hellooo
Prove that, sin2x+sin2y=2sin(x+y)cos(x-y).

we can short the solution by using the fact that $\sin (a)\cos (b)=\frac{\sin (a+b)+\sin (a-b)}{2},$ in our case put $(a,b)=(x+y,x-y)$ and the rest follows trivially.