SOLUTION: Simplify the expression by using a double-angle formula. 2cos^2 y/3-1

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Simplify the expression by using a double-angle formula. 2cos^2 y/3-1      Log On


   

Question 1012024: Simplify the expression by using a double-angle formula.
2cos^2 y/3-1
Answer by ValorousDawn(53) About Me  (Show Source):
You can put this solution on YOUR website!
Recall that cos%282x%29=2cos%5E2%28x%29-1
Set the equation equal to the one given.
2cos%5E2%28x%29-1=2cos%5E2%28y%2F3%29-1
x=y%2F3

Then substitute.
2cos%5E2%28x%29-1=cos%282x%29
2cos%5E2%28y%2F3%29-1=cos%282y%2F3%29