求证sina^2+sin&^2-sina^2*sin&^2+cosa^2*cos&^2=1
问题描述:
求证sina^2+sin&^2-sina^2*sin&^2+cosa^2*cos&^2=1
答
原式=sina^2+(sin&^2-sina^2*sin&^2)+cosa^2*cos&^2=sina^2+sin&^2(1-sina^2)+cosa^2*cos&^2=sina^2+(sin&^2*cosa^2+cosa^2*cos&^2)=sina^2+(sin&^2+cos&^2)*cosa^2=sina^2+cosa^2=1