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数学
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已知sina+sinb=1/3,sinb-cosa=1/2,求sin(a-b)的值
人气:430 ℃ 时间:2020-05-07 11:01:36
解答
sina+cosb=1/3,平方 sin^2a+2sinacosb+cos^2b=1/9
sinb-cosa=1/2,平方 sin^2b-2cosasinb+cos^2a=1/4 相加
2-2(sinacosb-cosasinb)=13/36
2-2sin(a-b)=13/36
sin(a-b)=59/72
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