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

I have fun with this website. It is very helpful and great. I have a question in geometry. I try to solve it but it needs imagination to figure out the point on the surface. This question makes me confused about other exercises. I hope someone solves this question. (I see this question needs a real expert in geometry.)

(Lambert's cylindrical projection) Consider the projection of $S^2−(0,0,\pm 1)$ onto a unit cylinder by radial projection; that is

$$\Pi: (x,y,z) \to( \frac{x}{\sqrt{x^2+y^2}}, \frac{y}{\sqrt{x^2+y^2}}, z)$$

Check that this map preserves area that it is not a conformal map. Thank you so much for helping. Good luck.

share|cite|improve this question
Oh, dear: please do use LaTex when writing mathematics in this site! Go to the FAQ section for diretions. – DonAntonio Feb 25 '13 at 12:24
Hint: What is the surface element on the sphere, in spherical coordinates $(\theta,\phi)$? And what is the surface element on the cylinder, in $(\theta,z)$ coordinates? Note that $z=\cos\phi$ and try to connect the two. As for non-conformality, check how infinitimal arclengths along the sphere map to the cylinder, in the latitudinal and longitudinal direction respectively. – Harald Hanche-Olsen Feb 25 '13 at 12:52

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.