1. The problem statement, all variables and given/known data Write the Trigonometric Expression as an algebraic expression. cos(2arccos 2x) 2. Relevant equations Probably the inverse properties, I'm not sure. 3. The attempt at a solution I know I can rewrite this equation as. u= arccos 2x cos(2cos u=2x) I can also say that the adjacent leg is 2x units long and the hypotenuse is 1 unit long. Then using the pythagorean theorm I can figure the opposite leg to be sqrt(1-4x2) I'm not sure If this is necessary though can someone point me in the right direction? The 2 in front of the arccos is throwing me off because if that wasn't there I would just use the inverse property and cos(arccos 2x) would equal 2x.