Sin 12pi/ 11+cos780 градус +sin25 pi/ 11 решить задачу

Question

Sin 12pi/ 11+cos780 градус +sin25 pi/ 11 решить задачу

Answer 1

Sin(π+π/11)+cos(720+60)+sin(2π+3π/11)=
=-sinπ/11+cos60+sin3π/11=(sin3π/11-sinπ/11)+1/2=
=2sinπ/11cos2π/11+1/2