Tg 1,8 * ctg 1,8+ ctg^2 (-(5п/6) - sin^2 п/6=-cos^2*п/6

Question

Tg 1,8 * ctg 1,8+ ctg^2 (-(5п/6) - sin^2 п/6=-cos^2*п/6

Answer 1

1+ctg(-5п/6)-sin^2п/6= cos^2 п/6
sin^2п/6+cos^2п/6-sin^2п/6= cos^2п/6
cos^2п/6= cos^2п/6