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Question
Prove the following.
tan4θ + tan2θ = sec4θ - sec2θ
Solution
Taking LHS
tan4θ + tan2θ
= tan2θ( tan2θ + 1)
= (sec2θ - 1)(sec2θ) [1 + tan2θ = sec2θ]
= sec4θ - sec2θ
= RHS
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