Limits and Riemann sums
One scale shrinks both the area slices and the local step, and the definite integral and the derivative both come out of a finite approximation.
5 pieces about this concept, across works, topic guides, and exam visualizations.
The secant slope approaches the tangent slope, so the derivative reads as an instantaneous rate of change.
Change the degree n and the center a, and watch the Taylor polynomial fit sin x, cos x, and e^x locally.
Compare f(x) with f'(x), and watch increase, extrema, and the tangent slope move together.
Drag a point in the plane and watch the gradient stay orthogonal to the level curve, pointing where the function increases fastest.