SOLUTION: I need to simplify 2cos^2(θ/3)-1 using a double-angle formula. I really can't figure it out, thank you!

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Question 1086276: I need to simplify 2cos^2(θ/3)-1 using a double-angle formula. I really can't figure it out, thank you!
Answer by Edwin McCravy(20062)   (Show Source): You can put this solution on YOUR website!


The double angle formula to use is this one

        

We substitute  for 

        

The right side of that equation is what we're given,
so the answer is the left side:

        

which can be also be written as

        or

       

Edwin
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