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標題:
cot 40(degrees) - tan 40(degrees) = 2tan10(degrees)
發問:
Urgent Please!
最佳解答:
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
cot 40(degrees) - tan 40(degrees) = 2tan10(degrees)
發問:
Urgent Please!
最佳解答:
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
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