A) arcsin(-1)/2 = -arcsin1/2 = -π/6.
arcsin1/2 = π/6.
arcsin√2/2 = π/4.
arcsin(-√3)/2 = -arcsin√3/2 = -π/3.
B) arccos1/(-√2) = π-√2/2 = π-π/4 = 3π/4.
arccos1/(-1) = arccos(-1) = π-0 = π.
arccos1/1 = arccos1 = 0.
arccos1/√2 = arccos√2/2 = π/4.
C) arctg1/√1/3 = arctg1/1/√3 = arctg1/√3/3 = arctg1/√3•1/3 = arctg1/3√3 = arctg√3 = π/3.
arctg1/√1 = arctg1 = π/4.
arctg1/√3 = arct√3/3 = π/6.