You are Here: Home >< Maths

# Torus Equation

1. Let T be a circle with diameter AC=a, and let B be a point on T such that AB=b<a. Let T' be the semicircle with diameter AC in the plane perpendicular to that of T.

Rotating T' around the perpendicular at A to the plane ABC generates a torus of internal radius 0. Give the equation of .
__

I've started by drawing everything out. If the circle is in the x-y plane, with the point A as at the origin, then the perpendicular is the z axis and the semi circle T' is in the x-z plane. Rotating around the z axis I can't see how this produces a torus? At best I get an upper half of a torus?
2. (Original post by miml)
At best I get an upper half of a torus?
Yep, that's what I make it.

Edit: There also seems to be redundant information there. Multipart question?
3. (Original post by ghostwalker)
Yep, that's what I make it.

Edit: There also seems to be redundant information there. Multipart question?
Thanks, I think what they want is to extend the semi-circle to a circle in the x-z plane, rotate it, give the equation of the resulting torus and then for the following parts only consider the upper half.

Archytas' solution to doubling the cube if you're interested.

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: October 23, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Is this true about Oxbridge?

Should I still go?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams