= sin^2(a) - sin(a)sin(b)sin(b) + sin^2(b)= sin^2(a) - sin(a)sin(b)sin(b) + sin^2(b)= sin^2(a) - sin^2(b) + sin^2(b)= sin^2(a)
= sin^2(a) - sin(a)sin(b)sin(b) + sin^2(b)
= sin^2(a) - sin(a)sin(b)sin(b) + sin^2(b)
= sin^2(a) - sin^2(b) + sin^2(b)
= sin^2(a)