Useful Mathematical Identities

2 + cos2 = 1 1 + tan2 = sec2 sin( − θ)
= − sinθ cos( − θ) = sinθ sin2θ
= 2sinθcosθ cos2θ = cos2 − sin2
= 2cos2θ − 1 = 1 − 2sin2θ 1 + cot2 = csc2 ejθ
= cosθ + jsinθ tan( − θ)
= cotθ