Question

y=sin^4x-cos^4x函数求导过程

Answer 1

y=sin^4x+cos^4x=[(sinx)^2+(cosx)^2]^2-2(sinxcosx)^2

=1-2(sinxcosx)^2

=1-[(sin2x)^2]/2

=1-[1-(cos4x)]/4

=(3+cos4x)/4

最大值=1

最小值=1/2

值域[1/2,1].