Find tan from sin: Interactive Geometric Demonstration

Find tan from sin: Interactive Geometric Demonstration
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2016-02-14 15:25
This GeoGebra example demonstrates how to derive the tangent (tan) of an angle from its given sine (sin) value using a unit circle and right-triangle construction. The core mathematical concept is the trigonometric identity tan = sin/cos, where cos is obtained from the Pythagorean relation on the unit circle. The construction uses commands such as Point, Circle, Intersect, OrthogonalLine, Vector, SurdText, Textfield, and InputBox1 to create an interactive environment: a unit circle, a movable point defining the angle, perpendicular lines forming a right triangle, and an input box where users can enter a sine value, causing the diagram and computed tangent to update dynamically. This is ideal for high school trigonometry lessons, helping students visualize the relationship between sine, cosine, and tangent, and for college preparatory review of trigonometric ratios.

GeoGebra Commands & Parameters

  1. Point(xAxis) → B
  2. Intersect(xAxis, yAxis) → A
  3. Circle(A, B) → c
  4. OrthogonalLine(S, yAxis) → a
  5. Intersect(c, a) → C, D
  6. OrthogonalLine(D, xAxis) → b
  7. Intersect(b, xAxis) → E
  8. SurdText(ta2) → ta2s
  9. SurdText(x(E)) → text51
  10. SurdText(y(S)) → sy
  11. OrthogonalLine(C, xAxis) → d
  12. Intersect(d, xAxis) → F
  13. SurdText(ta1) → ta1s
  14. SurdText(x(F)) → text5
  15. Textfield(s) → InputBox1
  16. Vector(D, E) → u
  17. Vector(C, F) → v
  18. SurdText(S) → text2
  19. SurdText(y(S)^(2)) → ssy
  20. SurdText(1 - y(S)^(2)) → assy

AI Drawing Prompt Reference

Draw a unit circle centered at the origin on a coordinate plane, with the circle intersecting the positive x-axis at a point. Place a movable point on the circle whose y-coordinate equals a user-specified sine value. From this point, drop perpendiculars to the x-axis and y-axis, forming a right triangle. Mark the foot on the x-axis and display its x-coordinate (the cosine). Include an input box for the sine value that updates the diagram. Also, take another point on the circle symmetric about the y-axis, drop a perpendicular to the x-axis, forming a second right triangle. Show vectors from the origin to the two feet on the x-axis)Skip. Display square-root expressions for the sine squared, one minus sine squared, and the coordinates, to illustrate that tangent equals sine over cosine.
The prompt above was compiled from the original drawing commands and is for reference only.