Definition of the Derivative – Tangent Slope and Limit Visualization

① This interactive GeoGebra example demonstrates the definition of the derivative by showing how the slope of a secant line approaches the slope of the tangent line as Δx tends to zero. ② The core mathematical concepts include the limit definition of the derivative, secant and tangent lines, and instantaneous rate of change. ③ Construction details: uses Line, Slope, Tangent commands, along with Textfield and InputBox for interactive input; a slider Δx controls the secant line's approach to the tangent; objects include function f, points A, B, C, slope value m, and related variables. ④ Suitable for high school and introductory college calculus students, this example helps visualize the transition from average to instantaneous rate of change and reinforces the concept of limits in differentiation.