This is part of the QCE Specialist Maths course. In this post, we learn to prove and solve double angle formulae for sine and cosine.
Here are the formulae:
Sine
sin(2x) = 2 sin(x) cos(x)Cosine
cos(2x) = cos^2(x) -sin^2(x) cos(2x) = 1 -2sin^2(x) cos(2x) = 2cos^2(x) -1Tangent
tan(2x) = \frac{2tan(x)}{1-tan^2(x)}
Double Angle Identities