# What does (cos(2x))^2 equal?

by justine411
Tags: cos2x2
 P: 16 1. The problem statement, all variables and given/known data (cos2x)^2 2. Relevant equations 3. The attempt at a solution I'm not sure if it is cos^2(2x) or cos^2(4x) or what. Should I use an identity to simplify it to make it easier to solve? Please help! :)
 P: 2,046 What is there to solve??? (cos2x)^2 is just an expression.
 Math Emeritus Sci Advisor Thanks PF Gold P: 39,503 In what sense is (cos(2x))2 a "problem"? What do you want to do with it? I will say that (cos(2x))2 means: First calculate 2x, then find cosine of that and finally square that result. Notice that it is still 2x, not 4x. The fact that 2 is outside the parentheses means that it only applies to the final result.
P: 14
What does (cos(2x))^2 equal?

 Quote by HallsofIvy In what sense is (cos(2x))2 a "problem"? What do you want to do with it? I will say that (cos(2x))2 means: First calculate 2x, then find cosine of that and finally square that result. Notice that it is still 2x, not 4x. The fact that 2 is outside the parentheses means that it only applies to the final result.
Doesn't (cos(2x))2 = cos2(2x)2 = cos2(4x2) ?