Results are out! Find what you Get quick advice or join the chat

Unlock these great extras with your FREE membership

  • One-on-one advice about results day and Clearing
  • Free access to our personal statement wizard
  • Customise TSR to suit how you want to use it

Torus Equation

Announcements Posted on
Find your uni forum to get talking to other applicants, existing students and your future course-mates 27-07-2015
  1. Online

    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  \mathcal{T} of internal radius 0. Give the equation of  \mathcal{T} .

    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. Offline

    (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. Online

    (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.


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  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
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

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.

Have you ever posted a picture of your food on social media?
Results and Clearing

Results are coming...

No sweat. Here's all you need to make sure you're ready

new on tsr

Join the American Society

Whether you're from the USA or just love it!

Study resources

Think you'll be in clearing or adjustment?

Hear direct from unis that want to talk to you

Get email alerts for university course places that match your subjects and grades. Just let us know what you're studying.

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.