tan(x/2)
= sin(x/2) / cos(x/2)
= 2sin(x/2) cos(x/2) / [ 2cos²(x/2) ]
= sinx / (1+cosx)哪个公式的？不懂！再讲详细一点这已经是完整的步骤了，请问哪一步不懂？跳转很大，下面两步都没看懂= 2sin(x/2) cos(x/2)/[ 2cos²(x/2) ]= sinx / (1+cosx)