Verify the identity: 1−cos(2θ)sin(2θ)=tan(θ)\frac{1 - \cos(2\theta)}{\sin(2\theta)} = \tan(\theta)sin(2θ)1−cos(2θ)=tan(θ).
Use double angle formulas and simplify
Graph both sides and see they coincide
This is not a valid identity
Use the Law of Sines