I recently came across a description of a unit circle's equivalency from center-radius to general form that looked quite odd to me. From a center radius form of (x-0)^2 + (y-0)^2 = 1^2 the equation went to (x^2)x + (y^2)y - 1 = 0. The -1 is quite obvious, but I can't figure out how the x and y terms converted to (x^2)x (y^2)y. Where did this additional x and y come from? To me that's x^3 & y^3. This MUST be a typo, right?