Question

求证tana/2=sia/1+cos=1-cosa/sina

Answer 1

tana/2=sin(a/2)/cos(a/2)=2sin(a/2)cos(a/2)/2cos²(a/2)=sin2*(a/2)/{2[1+cos2*(a/2)]/2}=sina/(1+cosa)tana/2=2sin²(a/2)/2sin(a/2)cos(a/2)=2[1-cos2*(a/2)]/sin2*(a/2)=(1-cosa)/sina