One of the questions in the homework for online precalc class I'm taking is to find the exact value for cos (67.5).(adsbygoogle = window.adsbygoogle || []).push({});

At first I didn't realize that I should just take the half angle of 135, so instead I tried to find the value for cos (45 + 45/2), and got stuck at this point.

If I calculate the actual value I get the correct answer, but I'm not able to see how I can simplify this further.

I know the solution is as simple as finding the half angle value of

Any suggestions of how I can get from my first attempt solution to the simpler (and correct) solution?

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# How to find the exact value of cos 67.5 ?

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