Volume of Revolution – Washers with Variable Axis

①This example demonstrates how to compute the volume of a solid of revolution when the axis of rotation is not a coordinate axis but a variable line, using the washer method. ②Core mathematical concepts include definite integrals in solid geometry, the washer method (integrating the area of annular cross-sections), and how the position of the rotation axis affects the integrand. ③Construction highlights: from the summary, the commands Segment and Circle are used, along with objects f, g, a, A, B, h, b, j, D, i, c, d, allowing dynamic adjustment of the axis to visualize changing washer radii. ④Suitable for advanced high school or introductory college calculus students, this serves as an interactive tool for understanding geometric intuition and integral formulation of volumes of revolution.