Let A = (1/2)(1+x2)[cos x (1 + sin x)-1/2 + 2x(1-x2)-1/2]
Let B = 2x[(1 + sin x)1/2 + (1 - x2)1/2]
The derivative sought then is (A - B)/[(1 + x2)2
Recently one of my classes taught me this little jngle:
Downsie d upsie - upsie d downsie divided by downsie squared