(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

How to get from

[tex]\sqrt{2+2cosx}[/tex]

to

2cos(x/2)

3. The attempt at a solution

I'm pretty much stuck on this.

I can only see that is simplifies by taking out the common factor 2, which isnt correct.

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# Trig identities?

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