Draw a Closed Plane Curve w/ Positive Curvature

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Homework Help Overview

The discussion revolves around the challenge of drawing a closed plane curve that maintains positive curvature while not being convex. Participants are exploring the characteristics of such curves and the implications of self-intersection.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are considering various shapes, such as a banana or a figure resembling the number 8, while questioning the conditions for positive curvature. There is also discussion about whether the curve can cross itself and the implications of convexity.

Discussion Status

The conversation is active, with participants sharing ideas and seeking clarification on the requirements for the curve. Some have offered hints and suggestions, while others express confusion about the relationship between curvature and self-intersection.

Contextual Notes

There is an ongoing debate about the definitions of convexity and positive curvature, as well as the constraints of the assignment. Participants are grappling with the concept of maintaining positive curvature while allowing for self-intersection.

Lee7
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Homework Statement



How can I draw a closed plane curve with positive curvature that is not convex

The Attempt at a Solution



I was thinking drawing it like a banana but more curved, will that do?
 
Last edited:
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Is it allowed to cross itself?
 
since it is not convex I think it can cross itself.
 
Lee7 said:

Homework Statement



How can I draw a closed plane curve with positive curvature that is not convex

The Attempt at a Solution



I was thinking drawing it like a banana but more curved, will that do?

A banana curve does not have positive curvature everywhere.
 
Ray - You are right! So how can I draw one that is positive curvature?
 
Lee7 said:
Ray - You are right! So how can I draw one that is positive curvature?

Well, that is your assignment!
 
Can you give a hint please?
 
If it were convex then it is just a sphere? But a non-convex with positive curvature is confusing me.
 
Lee7 said:
Can you give a hint please?

Lee7 said:
If it were convex then it is just a sphere? But a non-convex with positive curvature is confusing me.

You mean "circle". You were given a hint -- let the curve cross itself. Try it.
 
  • #10
Yup, I am meant circle. Will an number 8 satisfy it where the top is a bit more curved?
 
  • #11
No. As soon as you start curving the other way your curvature goes through zero.
 
  • #12
Wow, this is harder than I thought.
 
  • #13
So it must cross itself? Am I overthinking this?
 
  • #14
It isn't hard; it's almost trivial. Take a pencil and start drawing. Don't change curvature direction, use the hint, and close the curve.
 

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