## The Geometer's Sketchpad Spirograph Lab, Part 5

### Mike Riedy

TOC || Page 2 || Page 3 || Page 4 || Intro Lab

### Part 5: Math Studs and Studettes Only

Circles On Circles On Circles:

Okay, I hope that wasn't too bad. New let's get down and dirty.

You can use the sketch you were just working on. Follow the procedure outlined under SPIROGRAPH on pages 2 and 3 to create another circle which will rotate around Son of Bert. Draw a small circle in the lower left corner of the sketch. Label the point on the circle "Radius control 3". Put a point on the circle. Name the new point "Ernie".

Highlight the center of Ernie's circle, and Son of Bert. Choose 'Mark Vector "Son of Bert"' from the TRANSFORM menu. Highlight Ernie and his circle and choose "Translate" from the TRANSLATE menu. Name the new point that is created "Son of Ernie".

Highlight the following objects in the following order:

1. Ernie
2. Ernie's circle
3. Bert (not Son of Bert)
4. Bert's circle
5. Roger
6. Roger's circle

Choose "Animate" from the sub-menu under the "Action Button" under the EDIT menu. Click on "Animate". Another button should then appear on your sketch labeled "Animate". Change the label on the button to "Strange Trip". Highlight Son of Bert and turn off the trace on him. Highlight Son of Ernie and choose "Trace Point" from the DISPLAY menu. Change the color of Son of Ernie to green and double-click on "Strange Trip".

Is there a pattern to this tracing?

____________________________________________________

Use the relation from CUSPS AND PHASES. How does a change of radii affect the tracing?

_________________________________________________

_________________________________________________