Equation for circle points in 3D

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Discussion Overview

The discussion revolves around finding an algebraic formula to calculate the coordinates of points on a circle defined by three points (A, B, C) in 3D space. Participants explore methods to derive the circle's center and radius based on the positions of these points.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant proposes creating a triangle inscribed in a circle using points A, B, and C, and suggests calculating the lengths of the triangle's sides to find the radius.
  • Another participant asks if the coordinates of the circle's center can be expressed as a function of the positions of point A and the lengths of the sides connecting A to B and A to C.
  • A later reply emphasizes the importance of the bisector in the context of the problem, suggesting that the points must not be collinear to lie on a circle.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as multiple approaches and considerations are presented without resolution of the problem.

Contextual Notes

There are limitations regarding the assumptions about the positions of points A, B, and C, and the dependence on specific mathematical definitions and formulas for calculating the circle's properties.

Nikkki
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TL;DR
Calculate the coordinates of consecutive points based on ABC points lying on a circle in 3D space
Hello,

I am trying to solve a problem and I would like to ask for help.

I have 3 points (A, B, C) in 3D space that are assumed to be on a circle.

EXAMPLE 1
1637915795573.png
1637915918290.png
EXAMPLE 2
1637920200382.png
1637916124402.png

My goal is to create an algebraic formula to calculate the coordinates for 10 points on a circle composed of ABC points at any distance from each other.

1637916560383.png
1637916587355.png

MY IDEA

My first idea was to create a triangle inscribed in a circle from the ABC points and then the radius of the circle.
First, I calculate the lengths of the triangle's legs by recalculating the lengths of |AB| |AC| and |CB| vectors.

1637920433604.png

I calculate the radius length using the formula (https://www.physicsforums.com/threads/equation-of-a-circle-through-3-points-in-3d-space.173847/):
1637920084001.png

And at this step, I have now stopped
 
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The center has a distance r to all these points. Can you find its coordinates as function of e.g. a, (b-a) and (c-a), e.g. the position of a and two sides? This is completely analogous to the two-dimensional problem.
 
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mfb said:
The center has a distance r to all these points. Can you find its coordinates as function of e.g. a, (b-a) and (c-a), e.g. the position of a and two sides? This is completely analogous to the two-dimensional problem.
Thank you for your answer.
I am testing the formula for the circle center coordinates in the "Cartesian coordinates from cross- and dot-products" section on the website : https://en.wikipedia.org/wiki/Circu...sian_coordinates_from_cross-_and_dot-products
 
Hint: think bisector - the problem says 'lies on a circle' which has to imply that the points are not collinear.
 

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