Algebraic Determination of the Fermat-Torricelli Point

Algebraic Determination of the Fermat-Torricelli Point
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2026-04-06 07:07
This GeoGebra example demonstrates how to use algebraic methods to determine the Fermat-Torricelli point (Fermat point) in a triangle. The Fermat point is the special point inside a triangle that minimizes the sum of distances to the three vertices. Core mathematical concepts include: Fermat point theory (when all interior angles of a triangle are less than 120°, the Fermat point satisfies that the angles between any two connecting segments to the vertices are all 120°), trigonometry, area methods, and equation solving. Construction details: Use Polygon command to draw triangle ABC, use Line and Angle commands to construct 120° angle lines, use Intersect command to find the intersection point (Fermat point F), use Segment command to measure distances and verify that AF+BF+CF is minimized. Suitable for high school mathematics electives and geometry competition training, helpful for understanding the connection between optimization problems and geometric construction.

GeoGebra Commands & Parameters

  1. Polygon(A, B, C) → t1, c, a, b
  2. Polygon(A, B, 3) → poly1, f, g, h, D
  3. Polygon(B, C, 3) → poly2, i, j, k, E
  4. Segment(A, E) → l
  5. Segment(D, C) → m
  6. Intersect(m, l) → F
  7. Line(A, E) → n
  8. Line(D, C) → p
  9. Segment(B, F) → q
  10. Segment(A, F) → r
  11. Segment(C, F) → s
  12. Polygon(A, F, C) → t2, c_1, a_1, f_1
  13. Polygon(A, F, B) → t3, b_1, a_2, f_2
  14. Polygon(B, F, C) → t4, c_2, b_2, f_3
  15. Angle(C, F, B) → α
  16. Angle(B, F, A) → β
  17. Angle(A, F, C) → γ

AI Drawing Prompt Reference

Draw a triangle ABC with a point F inside. F is the point that minimizes the sum of distances AF+BF+CF. First, draw triangle ABC. Then, draw line segments from A to E and from D to C; their intersection is F. Next, draw segments from B to F, A to F, and C to F, and verify that they satisfy 120-degree angle conditions. Ensure the diagram is clear and labels key points like A, B, C, and F.
The prompt above was compiled from the original drawing commands and is for reference only.