sin2x=cos2x+1,则cos2x等于在线等

问题描述:

sin2x=cos2x+1,则cos2x等于
在线等

sin2x=cos2x+1
2sinxcosx = 2(cosx)^2
cosx( cosx - sinx )=0
cosx =0 or cosx = sinx
cos2x= (cosx)^2 - (sinx)^2
= 0 or -1