设x=sinα-4cosαx=sinα+2cosα-4cosα=1/6-4cosαsina+2cosα=根号(1-cosa^2)+cosa=1/6 根号(1-cosa^2)=1/6-cosa1-cosa^2=1/36-cosa/3+cosa^22cosa^2-cosa/3-35/36=0cosa=[1/3±根号(1/81+70/9)]/4=[1/3±根号(631...