3 ms·

And also the surface area of a spherical zone, as shown here: http://mathworld.wolfram.com/Zone.html http://mathworld.wolfram.com/Zone.html

• svrocks 15y ago
  wow that's an interesting and counterintuitive result. I need to figure out why my integral doesn't line up with that
• svrocks 15y ago
  After choosing a different way to find the angle, my answer matches yours. Kudos for having a much simpler answer.