设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于?
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![设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于?](/uploads/image/z/990098-26-8.jpg?t=%E8%AE%BEx%E4%B8%BA%E9%94%90%E8%A7%92%2C%E8%8B%A5cos%28x%2B30%C2%B0%29%3D4%2F5+%2Csin%282x%2B15%C2%B0%29%E7%AD%89%E4%BA%8E%3F)
设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于?
设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于?
设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于?
解决方案,cosxcos30°-sinxsin30°+的sinx = 0/5
√3/2cosx 1 / 2sinx = 0/5
COS(X-30°)= 8/10
COS(X-60°)= COS2(X-30°)= 2cos ^ 2(X-60°)-1 = 2 *(4/5)^ 2 = 7/25