Rotating a Parabola Around the y-axis

Drag point A (the [color=#00FF00]GREEN[/color] point) and see the result of rotating the parabola [math]f(x)=4x−x^{2}[/math] around the y-axis.
Rotating a Parabola Around the y-axis
– Steve Phelps

Information: Rotating a Parabola Around the y-axis