Question

Пожалуйста, помогите)) Ctg13/12pi - ctg 5/12 pi

Answer 1

Ctg13π/12-ctg5π/12=ctgπ/12-ctg5π/12=sin(π/12-5π/12)/sinπ/12*sin5π/12=
=-sinπ/3:1/2(cos(π/12-5π/12)-cos(π/12+5π/12))=-√3/2 :1/2(cosπ/3-cosπ/2)=
=-√3/2:1/4=-2√3