URGENT F4 TRIGONOMETRY
回答 (1)
2011-02-21 8:16 am
✔ 最佳答案
(2cos^2(90-x)-1)/(cos(90-x)-cosx)=(2sin^2(x)-1)/(sinx-cosx)
=(2sin^2(x)-(sin^2(x)+cos^2(x)))/(sinx-cosx)
=(sin^2(x)-cos^2(x))/(sinx-cosx)
=[(sinx-cosx)(sinx+cosx)]/(sinx-cosx)
=sinx+cosx
收錄日期: 2021-04-22 00:54:15
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