已知sin^2X+sinX=1,求cos^4X=cos^2X的值
问题描述:
已知sin^2X+sinX=1,求cos^4X=cos^2X的值
答
sin^2X+sinX=1,sinX=1-sin^2X=cos^2X cos^4X=sin^2X
cos^4X=cos^2X中间应该是+?
cos^4+cos^2X=sin^2X+cos^2X=1