证明：sina=sin(a/2*2)=s*sin(a/2)*cos(a/2)cosa=cos(a/2*2)=(cos(a/2))^2-(sin(a/2))^2把sina,cosa代入：(1+sinα)/cosα=(sin(a/2)+cos(a/2))^2/(sin(a/2)-cos(a/2))/(sin(a/2)+cos(a/2))=(sin(a/2)+cos(a/2))/(si...