Question

sina+sina^2=1,化简cosa^2+cos^6+cosa^8

Answer 1

sina+sina^2=1,cosa^2+sina^2=1得sina=cosa^2带入cosa^2+cos^6+cosa^8=sina（1+sina^2+sina^2cosa^2）=sina[2-sina+(1-sina)sina]=sina(2-sina^2)=sina(1+sina)=1.计算完毕.