来自郭世颖的问题
问一道数学题,已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sin(3π/4+β)=5/13,求sin(α+β)的值
问一道数学题,
已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sin(3π/4+β)=5/13,求sin(α+β)的值
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2020-07-27 15:12
问一道数学题,已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sin(3π/4+β)=5/13,求sin(α+β)的值
问一道数学题,
已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sin(3π/4+β)=5/13,求sin(α+β)的值
cos(π/4-α)=3/5所以sin(π/4-α)=-4/5,根据α的范围确定正负sin(3π/4+β)=5/13所以cos(3π/4+β)=-12/13根据β的范围确定正负sin(α+β)=sin[(3π/4+β)-(π/4-α)-π/2]=-cos[(3π/4+...