First, we can simplify the expression by using the difference identity for sine: sin(pi - a) = sin(a) and the difference identity for cosine: cos(pi/2 - a) = sin(a).

Therefore, the expression becomes:
2sin(a)cos(a) = sin(2a)

So, 2sin(pi-a)cos(pi/2-a) simplifies to sin(2a).