cot 40(degrees) - tan 40(degrees) = 2tan10(degrees)
回答 (1)
2007-09-15 6:39 pm
✔ 最佳答案
要用amaths的公式let x=40
L.H.S
=cotx-tanx
=(cos^2x-sin^2x)/cosxsinx
=2cos2x/sin2x
=2cot2x
=2tan(90-2x)
put x=40
=2tan10
=RHS
收錄日期: 2021-04-13 13:29:21
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