Parametric Intersection of a Sphere and a Plane (Circle)

Parametric Intersection of a Sphere and a Plane (Circle)
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2023-07-26 17:15
This example demonstrates how to construct and visualize the intersection curve (typically a circle) of a sphere and a plane in 3D space using parametric equations. Core mathematical concepts include spatial analytic geometry, sphere and plane equations, solving intersection of surfaces, and parametric curve representation. The construction uses GeoGebra commands such as Vector, Line, Intersect, Transpose, ReducedRowEchelonForm, UnitVector, and CurveCartesian to compute the foot of perpendicular from the sphere center to the plane, the distance, and orthonormal basis vectors within the plane, then generate the parametric circle. Suitable for senior high school or early university students learning spatial geometry and parametric equations, and for teachers demonstrating dynamic 3D intersections in class.

GeoGebra Commands & Parameters

  1. Vector(Point[l1]) → u
  2. Line((x(A), y(A), z(A)), Vector[(x(u), y(u), z(u))]) → f
  3. Intersect(f, p) → B
  4. Transpose(Join[{{l1}, Identity[3]}]) → m1
  5. ReducedRowEchelonForm(m1) → m2
  6. UnitVector(Point[Take[m2(3), 2, 4]]) → v
  7. CurveCartesian(B + ((g * cos(t)) * v) + ((g * sin(t)) * w), t, 0, (2 * pi)) → circ

AI Drawing Prompt Reference

Create a 3D plot of the intersection curve between a sphere and a plane, typically a circle, represented parametrically. Start by using the sphere’s center and the given plane to determine the foot of the perpendicular from the center to the plane. Compute two orthonormal direction vectors lying in the plane, then form points on the intersection by taking the perpendicular foot as the reference point and adding the sphere-plane distance (as the radius scale) times cos(t) along the first direction and sin(t) along the second direction. Render the resulting parametric curve as t varies from 0 to 2π.
The prompt above was compiled from the original drawing commands and is for reference only.