(1 - 2sin^2 2x) /(1 - sin4x) = (1 + tan2x )/(1 - tan2x); sin4x + cos4x = 3/4 + 1/4 cos4x

a) (1 - 2sin^2 2x) /(1 - sin4x) = (1 + tan2x )/(1 - tan2x)
b) sin4x + cos4x = 3/4 + 1/4 cos4x