已知sin(X+Y)=2/3,sin(X-Y)=1/5,求(tanX)/(tanY)的值
人气：286 ℃ 时间：2020-03-19 11:14:15
解答
(tanX)/(tanY)=（sinX/cosX）/(sinY/cosY)=(sinXcosY)/(cosXsinY)又sinXcosY=（1/2）[sin(X+Y)+sin(X-Y)]=（1/2）[(2/3)+(1/5)]=13/30cosXsinY=（1/2）[sin(X+Y)-sin(X-Y)]=（1/2）[(2/3)-(1/5)]=7/30代入原式,得(ta...
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