Prove that the following is an identity.
3-2cos^2 θ= 1+2cos^2(90-θ)
PLZ
Trigonometry 的 Prove 快少少
2009-10-11 6:09 pm
回答 (1)
2009-10-11 6:15 pm
✔ 最佳答案
3-2cos^2 θ= 1+2cos^2(90-θ)R.H.S.
= 1 + 2sin^2 θ (cos(90 - θ) = sinθ)
= 1 + 2(1 - cos^2 θ)
= 1 + 2 - 2cos^2 θ
= 3 - 2cos^2 θ
= L.H.S.
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