Question

Найти решение
sin (1/2arctg 3/4 - 2arccos 1/√5)

Answer 1

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