若(1-cosa)/(4+sin^2a)=0.5,求tana

问题描述:

若(1-cosa)/(4+sin^2a)=0.5,求tana

设cosa=x
(1-x)/(4+1-x^2)=0.5
x^2-2x-3=0
x=-1或x=3
但-1sin^2a的意思是sina的平方。谢sin^2a=[sin(a)]^2=1-[cos(a)]^2tana=?tan(a)=0啊