Define Circle Knowing Two Points and ARC LENGTH Only.

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Discussion Overview

The discussion revolves around determining the equation of a circle given two points on its circumference and the arc length between them. The context appears to involve applications related to bending beams, where the geometry of the circle is critical for understanding the shape of the beam.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in finding the equation of the circle with the given parameters and acknowledges the existence of two solutions based on curvature.
  • Another participant questions the need for additional context and suggests that the problem can be approached using the known chord length and arc length.
  • A third participant mentions having found two methods to solve the problem: one using Newton's approximation method and the other using Taylor expansion, providing links to resources for further exploration.
  • One participant suggests that the method requiring Newton's Method is the most straightforward approach to the problem.
  • A later reply indicates that knowing the two fixed points on the circumference provides both the arc length and the chord length, implying a relationship that could aid in solving the problem.

Areas of Agreement / Disagreement

Participants appear to have differing views on the necessity of additional context for the problem. While some agree on the methods available for solving the problem, there is no consensus on a single approach or solution.

Contextual Notes

Participants reference specific mathematical methods and resources, but there is no resolution on the effectiveness or applicability of these methods to the problem at hand. The discussion remains focused on exploring potential solutions without definitive conclusions.

Ryank
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I am having trouble doing exactly what the title says. I have two points and the arc length between them (this is a bending beam type of a situation). Essentially I know where the ends of the beam are and how long the bent beam is and I need to get the equation of the circle. And yes I realize there would be two distinct solutions depending on positive of negative curvature. Any help would be amazing, thanks!
 
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Ryank said:
I am having trouble doing exactly what the title says. I have two points and the arc length between them (this is a bending beam type of a situation). Essentially I know where the ends of the beam are and how long the bent beam is and I need to get the equation of the circle. And yes I realize there would be two distinct solutions depending on positive of negative curvature. Any help would be amazing, thanks!

What is the context of the question? Could you post a sketch? Thanks.
 
There doesn't really need to be a context. You know the length of a chord on the circle and the length of the arc segment between them. I did some digging and did finally manage to find two solutions. One uses Newton's approximation method and the other uses and taylor expansion:

http://norman.rasmussen.co.za/24/radius-from-arc-and-chord-length/
http://www.mathforum.com/dr.math/faq/faq.circle.segment.html#1
 
Last edited by a moderator:
Looks like case 1 from Dr. Math that requires Newton's Method is the most straightforward.
 
Last edited:
Perhaps this sketch will help, it's basic trigonometry.

Since you have fixed two points on the circumference you not only know the arc length you also know the chord length.
 

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