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※ 引述《IamCuteGirl (CuteGirl5566)》之銘言: :           1 1 : 設 cosθ=tanθ,則 _________ + _________ = : 1+sinθ 1-sinθ ______________ : 不好意思 上來麻煩大家了... sinθ cosθ = tanθ = ------- => (cosθ)^2 = sinθ cosθ 1 - (sinθ)^2 = sinθ (sinθ)^2 + sinθ - 1 = 0 -1 ±√5 sinθ = ---------- 2 -1 + √5 ∵ |sinθ|≦1 ∴ sinθ = ---------- 2 1 1 ----------- + ----------- 1 + sinθ 1 - sinθ 1 - sinθ + 1 + sinθ = ------------------------ (1 + sinθ)(1 - sinθ) 2 = --------------- 1 - (sinθ)^2 2 = ----------- (cosθ)^2 2 = ------- sinθ 2 = -------------- (-1 + √5)/2 4 = --------- √5 - 1 (4)(√5 + 1) (4)(√5 + 1) = -------------------- = -------------- = √5 + 1 (√5 - 1)(√5 + 1) 5 - 1 -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 111.250.168.29 ※ 文章網址: http://www.ptt.cc/bbs/Math/M.1406121489.A.013.html
IamCuteGirl :大大 感謝@___@ 07/23 21:34
※ 編輯: LuisSantos (111.250.168.29), 07/23/2014 21:55:53