Question

Решите
arccos(sin680°)

Answer 1

sin680=  sin(720  -  40)=  sin(-40)=  -sin40
arccos(-sin40) ----- (0≤α≤π)
sin 40 = 0.6428
-sin 40 = -0.6428

arccos(-0.6428 ) = $pi - arccos(0.6428 )$