1. The problem statement, all variables and given/known data Prove the Identity: tan²θ - sin²θ = tan²θsin²θ 2. Relevant equations 3. The attempt at a solution Well I got up to (sin²θ/cos²θ) - (sin²θcos²θ/cos²θ) = sin⁴θ/cos²θ I got the answer cause my calculator says sin²θ - sin²θcos²θ = sin⁴θ But I don't know how sin²θ - sin²θcos²θ = sin⁴θ. How do you subtract sin²θcos²θ with sin²θ? Also while I'm at it, how does sin⁴θ - cos⁴θ = 1 - 2cos²θ?