Derivatives allow us to solve real-world problems involving rates of change. Calculate derivatives of parametric functions. Methods for calculating derivatives of real-valued functions can be extended to parametric functions. For a curve defined parametrically, the value of dy/dx at a point on the curve is the slope of the line tangent to the curve at that point. dy/dx, the slope of the line tangent to a curve defined using parametric equations, can be determined by dividing dy/dt by dx/dt , provided dx/dt does not equal zero.