Question

函数y=sin^4x+cos^4x的值域是?

Answer 1

y=sin^4x+cos^4x

=(sin^2x+cos^2x)-2sin^2xcos^2x

=1-(sin2x)^2/2

=[2-(sin2x)^2]/2

=[4-2(sin2x)^2]/4

=(3+cos4x)/4

值域是:[1/2,1]