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## Homework Statement

I am looking for an angle, using Law of Cosines. I am trying to solve for C.

## Homework Equations

R^2= a^2+b^2- (2 X a X b X cos C)

## The Attempt at a Solution

These are the numbers I am using, plugged into the Law of Cosines:

80^2= 450^2+ 373^2-(2 X 450 X 373 X cos C)

I have solved this far, Cos C= -.999

I know it's right this far, because my teacher told me it was, but I don't know how to find the angle past this point. I know I have to use inverse of cosine somehow. Please, help me, test tomorrow. Thanks.:)