trig
posted by Master chief .
I get that we have to put it into radical form, but I don't understand the process. Can someone walk me through it and explain it?
arccos(1/2)

you want the angle Ø so that
cosØ= 1/2
We know that if the cosØ is negative, then Ø is in either the II or III quadrant
we also know that cos 60° =+1/2
so Ø = 18060 or 180+60
Ø = 120° or 240°
in radians it would be 2π/3 or 4π/3
your calculator will only give you the angle closest to the origin,
inter
2nd
cos
.5
=
and you will get 120 if your calculator is set to degrees. 
(12x2.17)
cos0 120.6