Identify Identities with pi & Theta: Precalculus Help

[Rosita]

Homework Statement

How do I put the sign for pi and the sign for theta? I can not solve this problem.
Please help because I am new and I am having difficulty in my precalculus homework. The problem says identify identities of: sin (pi/2 + theta) = cos theta

Homework Equations

The Attempt at a Solution

 

[rock.freak667]

Do you know how to expand sin(A+B) ?