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Help! I just know the answer will be simple.

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I have forgotten how to undo a cosine.

I'm working on a problem using the Law of cosines and I'm at the very last step. But I can't for the life of me remember how to undo a cosine.

My equation has whittled down to:

cos(x)=0.1049

I have the answer book next to me; but, no matter what I do, I can't get the same answer.
 Jan 20, 2014

2+0 Answers

 #1
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Hey Nobody Special

I remember that to undo a cosine you use the arccos of your answer. I think you'll have to put it into a calculator to get your answer because the only other way I know how to do it is by drawing right triangles which I'm not sure will be simple with the number you got for your cosine.
Hope this helps.
 Jan 20, 2014
 #2
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Man, that's the first thing I tried. Granted, I tried it on a different calculator. But I typed in cos^-1 (0.1049)

Anywho, thanks, Walt!
 Jan 20, 2014

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