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).
This is not a valid identity
Graph both sides and see they coincide
Use double angle formulas and simplify
Use the Law of Sines