sin^2 2x+sin2xsinx+cos2x=1 x在第一象限,求cos x/2的值

问题描述:

sin^2 2x+sin2xsinx+cos2x=1 x在第一象限,求cos x/2的值

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)...