Stephanie K. Lewis

EMAT 6680

A6#9

9. A parabola is the set of points equidistant from a line, called the directrix, and a fixed point, called the focus. Assume the focus is not on the line. Construct a parabola given a fixed point for the focus and a line (segment) for the directrix.

a. Use an Action Button to generate the parabola from an animation and trace of a constructed point.

b. Repeat 9a with a trace of the tangent line at the constructed point.

c. Use the locus command to generate the parabola from a constructed point or the tangent line at that point.

Using the Sketchpad to construct a parabola was more difficult than it appeared. Investigation, without direction to appropriately use the sketching tool was frustrating and time-consuming. This was a worthwhile exercise however. If I ever use the Sketchpad in a classroom situation, I will be sure to have a "how – to" guide handy!!!!

When constructing the parabola, I found it easier to use the locus command to generate the parabola from a constructed point. The hardest part was the actual construction. Once the construction of the point, directix and focus was done, it was a matter of selecting the key components for the locus command to work.