Good ol' trig: that bastion of angles and triangles is essential to calculating velocity, ... Maybe you can use the double angle formula and you don't have a problem with trig identities.

Double angle formulas are named so because they involve trigonometric functions of double angles, i.e., sin2θ, cos2θ and tan2θ. There are three main double angle formulas as below: where θ is ...

Revise trigonometric ratios of sine, cosine and tangent and calculate angles in right-angled triangles with this Bitesize GCSE Maths Edexcel guide.