# trig

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)

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1. 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 = 180-60 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.

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2. (12x2.17)
cos0 120.6

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