Verified answer

You could use the following formula

sin(A-B) = (sinA)(cosB) - (cosA)(sinB)

Let x = theta

sin(pi/2 - x) = (sin(pi/2))cosx - (cos(pi/2))(sinx)

= (1)(cosx) - (0)(sinx) = cos x

Now, cosine is an odd function meaning cosx = cos(-x).

sin(A+B)=sinAcosB+cosAsinB