sin^2 2x+sin2xsinx+cos2x=1 x在第一象限,求cos x/2的值
人气：498 ℃ 时间：2020-06-23 10:31:42
解答
sin²(2x)+sin(2x)sin(x)+cos(2x)=1sin²(2x)+sin(2x)sin(x)+1-2sin²(x)=1sin²(2x)+sin(2x)sin(x)-2sin²(x)=0[sin(2x)+2sin(x)][sin(2x)-sin(x)]=0sin(2x)+2sin(x)=01-2sin²(x)+2sin(x)...
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