Найти решение

sin (1/2arctg 3/4 - 2arccos 1/√5)

Ctg (arccos (-1/3)) = 1/tg (arccos (-1/3)) = 1/tg (П+argtg (√ (1-1/9) / (-1/3))) = 1/tg (arctg ((√8/9) / (-1/3))) = - √2/4;

sin (2arccos1/4) = 2sin (arccos1/4) cos (arccos1/4) = 2*1/4*sin (arcsin√ (1-1/16)) = 1/2*√154=√15/8