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# trig question

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Compute $$\cos \left( \frac{45^\circ}{2} \right)$$

Jul 29, 2020

#1
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For this, we can use half angle formulas. Since 45 degrees is a common angle on the unit circle, we can easily see that it's sine and cosine is $$\frac{\sqrt 2}{2}$$. Using the half angle formula for cosines, which is: $$\cos \frac{A}{2}=\pm \sqrt{\frac{1+\cos A}{2}}$$, we can get our answer.

Here is what you should do:

Plug in $$\frac{\sqrt 2}{2}$$ for cos A and solve.

Good luck!

Jul 29, 2020