証明cos^2(A-B)-cos^2(A+B)=sin2Asin2B
請詳列步驟
a math三角函數
2008-03-03 4:26 am
回答 (1)
2008-03-03 4:34 am
✔ 最佳答案
L.H.S = cos^2(A-B)-cos^2(A+B)= [cos(A - B) - cos(A + B)][cos(A - B) + cos(A + B)
= [cosAcosB + sinAsinB - (cosAcosB - sinAsinB)][cosAcosB + sinAsinB + cosAcosB - sinAsinB)]
= (2sinAsinB)(2cosAcosB)
= (2sinAcosA)(2sinBcosB)
= 2sin2Asin2B
= R.H.S
2008-03-02 20:35:28 補充：
= (2sinAcosA)(2sinBcosB)
= sin2Asin2B
尾二果句打多左個2,
應為
sin2Asin2B
收錄日期: 2021-04-23 22:27:34
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