1) cos^2a - cos^2b = (cos(a) + cos(b))(cos(a) - cos(b))
2) 3/4 - sin^2x = (3/2 - sin(x))(3/2 + sin(x))
1) cos^2a - cos^2b = (cos(a) + cos(b))(cos(a) - cos(b))
2) 3/4 - sin^2x = (3/2 - sin(x))(3/2 + sin(x))