Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

In certain math problem the only information about pyramid with quadrilateral base is that you can inscribe sphere inside. What kind of constraints was put on my pyramid ABCDS?

Is it something similar to situation where requirement to inscribe circle inside quadrilateral ABCD is that |AB| + |CD| = |BC| + |DA|?

share|cite|improve this question
If you have a sphere touching all five faces, then its center has to lie on the bisecting planes of all dihedral angles. So all these planes have to meet in a single point. I assume that you'll want more explicit requirements, but perhaps this will give you a start. – MvG Oct 21 '12 at 13:12

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.