Hi, I need help trying figure out this problem: I'm trying to figure out the steps to get from one equation to another

Starting Equation:

Y = X (cos^2Ɵ) (cos^2(π/2 - Ɵ)

**missing steps**

Final Equation:

Y = (X/4) sin^2(2Ɵ)

If anyone can help I'd greatly appreciate it. Thanks!