1. The problem statement, all variables and given/known data The problem asks us to find the equation for an isotropic oscillator in the form of an equation for an ellipse. I'm in PHYS 212, Analytic Mechanics. 2. Relevant equations x=Acost(ωt) y=5Acos(ωt-.6435) The equations I found for x and y. 3. The attempt at a solution So far I have the equation at y=5[x*cos(-.6435)+(1-x^2)^(1/2)*sin(-.6435)] I looked in the example in the text for the original derivation, and it basically skips through this part. I need to know how to transpose the equation I got to further simplify my work.