1. The problem statement, all variables and given/known data For the functions: x = r*cos(θ) y = r*sin(θ) Calculate dθ/dX * dX/dθ (considering θ as a function of x, y) and simplify. 3. The attempt at a solution I believe this should always be 1, by definition (as the product of a derivative and its inverse). However, I don't know how to show this. Solving the first function for θ, I get cos-1(x/r). The derivative of this is a relatively messy expression 1 over the product of r and a square root, and its being multiplied by something relatively simple (-r*sin(θ)). Why is it that this would simplify to 1? I get that the negatives and the r's will cancel. So it simplifies to: sin(θ) / √(1 - x2/r2) But I can't get any further nor am I satisfied that this expression is or is not equal to 1. Thanks in advance.