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

Would anybody shed some light on question 2.11 in Wilson's Curved Spaces?

The numbers $p,q\in \hat{\mathbb{C}}$ are stereographic projections of points $P,Q$ on the unit sphere. The spherical distance between $P$ and $Q$ is $d$. The reader is asked to show that The cross-ratio of the four points $\{p,q,\bar{p}^{-1},\bar{q}^{-1}\}$ in some order is equal to $-\tan^2(d/2)$

(I am so sorry about the previous typos, I am typing on my phone.)

share|cite|improve this question

Your Answer

 
discard

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

Browse other questions tagged or ask your own question.