求函数y=7-4sin(x)cos(x)+4cos^2(x)-4cos^4(x)值
问题描述:
求函数y=7-4sin(x)cos(x)+4cos^2(x)-4cos^4(x)值
答
y=7-4sin(x)cos(x)+4cos^2(x)-4cos^4(x)
=7--4sin(x)cos(x)+4cos^2(x)sin^2(x)
=7-2sin(2x)+sin^2(2x)
=(sin(2x)-1)^2+6
=6