Implicit differentiation

What is implicit differentiation?

Implicit differentiation differentiates equations where y is not isolated, e.g. x² + y² = 25. Treat y as a function of x and apply the chain rule whenever you differentiate a y term — d(y²)/dx becomes 2y · dy/dx. Used heavily for circles, ellipses and tangent/normal problems where rearranging to y = f(x) is impractical.