Question

(1 + ctg15°)/(1 - ctg15°) = ?

Answer 1

(1+сos15/sin15):(1-cos15/sin15)=(sin15+cos15)/sin15*sin15/(sin15-cos15)=
=(sin15+cos15)/(sin15-cos15)=(sin15+cos15)(sin15-cos15)/(sin15-cos15)²=
=(-cos30)/(1-sin30)=-√3/2:(1-1/2)=-√3