y= 4cos2x+4 sinxcosx-2=

问题描述:

y= 4cos2x+4 sinxcosx-2=

y= 4cos2x+4 sinxcosx-2
=4cos2x+2 sin2x-2
=2*(根号5)[(2根号5/5)cosx+(根号5/5)sinx]-2
=2*(根号5)sin(x+a)-2
a=arcsin(2*根号5/5)