(1+sina -cosa )/(1+sina +cosa ) =2 ,求 cosa 的值.
问题描述：
(1+sina -cosa )/(1+sina +cosa ) =2 ,求 cosa 的值.
求过程.
答
(1-cosa+sina)/(1+cosa+sina)=2[2sin²(a/2)+2sin(a/2)cos(a/2)]/[2cos²(a/2)+2sin(a/2)cos(a/2)]=2[2sin(a/2)(sin(a/2)+cos(a/2))]/[2cos(a/2)(sin(a/2)+cos(a/2))]=2sin(a/2)/cos(a/2)=2,所以tan(a/2)=2...