Prove:
cos2x+sin3x-cos4x = 4sin3xsin(6x+pie)/12cos(6x-pie)/12
求完整解
A.maths trigonometry 問題(急)
2010-08-03 2:06 am
回答 (1)
2010-08-03 2:24 am
✔ 最佳答案
L.H.S.4 sin3x sin(6x + π)/12 cos(6x - π)/12= 4 sin3x (1/2)(sin x + sin π/6)= 2 sin3x (sinx + 1/2)= 2 sinx sin3x + sin3x= 2 (-1/2)(cos4x - cos (2x)) + sin3x=(cos 2x - cos 4x) + sin3x= cos2x + sin3x - cos4x = R.H.S.
收錄日期: 2021-04-21 22:13:47
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