若sinx+sin^2x=1,则cos^2x+cos^4x=?
问题描述:
若sinx+sin^2x=1,则cos^2x+cos^4x=?
答
由 sinx+sin^2x=1
得 sinx=1-sin^2x=cos^2x
cos^2x+cos^4x
=cos^2x(1+cos^2x)
=sinx(1+sinx)
=sinx+sin^2x
=1