How do you calculate Arccos (sin (pi/6))?

Find ##arccos(sin (pi/6))##
Ans: ##+- pi/3##
##sin (pi/6) = 1/2##
therefor ##arccos (sin(pi/6)) = arccos (1/2)##
On the trig unit circle
##cos x = 1/2## –> arc ##x = +- pi/3##