I'm doing a project for my calculus class where we are determining the volume and surface area of a torus.The question I am on is asking me to find the allowable values of "R' and 'r' in the equation y=Sqrt[(r^2 - (x - R)^2)]. It gives us the manipulate shown below, but it does not work. I can manipulate "R" just fine, but when I try to move "r," the picture disappears. Could somebody tell me if this is typed in wrong? Or is there another way to solve this problem?
What I typed in:
Manipulate[
ParametricPlot3D[
{(R + r Cos[\[Alpha]]) Cos[\[Theta]], (R +
r Cos[\[Alpha]]) Sin[\[Theta]], r Sin[\[Alpha]]}, {\[Alpha], 0,
2 \[Pi]}, {\[Theta], 0, 2 \[Pi]},
PlotPoints -> 50, ImageSize -> Small, Mesh -> None,
{Axes -> False, Boxed -> False}, PlotStyle -> Brown,
ImageSize -> 200],
{R, 0.2, 0.629961}, {r, 0.2, radiusr}]
Attachments: