(sin15°-cos15°)/(sin15°+cos15°)的值
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(sin15°- cos15°)/(sin15°+ cos15°)
= (sin15°- cos15°)²/[(sin15°+ cos15°)(sin15°-cos15°)]
= (sin²15°+ 2sin15°cos15°+ cos²15°)/(sin²15°- cos²15°)
= (1 + sin30°)/(-cos30°)
= (3/2)/(-√3/2)
= -√3
= (sin15°- cos15°)²/[(sin15°+ cos15°)(sin15°-cos15°)]
= (sin²15°+ 2sin15°cos15°+ cos²15°)/(sin²15°- cos²15°)
= (1 + sin30°)/(-cos30°)
= (3/2)/(-√3/2)
= -√3
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