If \tan(\alpha/2) = m, then evaluate \frac{1-2\sin^2(\alpha/2)}{1+\sin\alpha} How to evaluate this?

dooporpplauttssg

dooporpplauttssg

Answered question

2022-04-22

If tan(α2)=m, then evaluate 12sin2(α2)1+sinα
How to evaluate this?

Answer & Explanation

j3jell5

j3jell5

Beginner2022-04-23Added 17 answers

Hint. Note that by the addition formula for the cosine
cosα=cos(α2+α2)=cos2(α2)sin2(α2)=12sin2(α2)
which implies that 2sin2(α2)=1cos(α)
Then use the tangent half-angle substitution (which follows from your formula m2=1cosα1+cosα
cosα=1m21+m2,sinα=2m1+m2

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