Investigating Geometry with GeoGebra

Henrico County Public Schools

Finding the Area of a Trapezoid

READ the instruction below and INTERACT with the GeoGebra applet on the right.

  1. Move the points B and D, to make a new trapezoid. Next move the green point.

  2. What shape is formed and how do you find its area?

  3. How the height of the trapezoid compare to the height of the new figure?
    Is this true any of the two figures? Why?

  4. How do the base lenghts of the two figures compare?

  5. How is the area of a trapezoid related to the area of the shaded figure?

  6. Using this information, what would be a formula for finding the area of a trapezoid?
    Test your formula using the applet.
Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and activated. (click here to install Java now)