Tangent Circles

By: Kimberly Young and Mindy Swain


Assignment # 7:

Given two circles and a point on one of the circles. Construct a circle tangent to the two circles with one point of tangency being the designated point.

We chose to do problem #1 and constuct a script tool for this problem.

The following link will give you the GSP file with the tool. Click here.

In order to constuct a tangent circle for the two given circles (green), we first place a point on the big circle,B, and made a line connecting this point with the center of the big circle. Next we made a new cicle with center B and the same radius as the small circle (circle A). Then we made a segement from A to C and found its midpoint. We constructed a perpendicular line through that midpoint. This gave us point D, around which we constructed a circle that is tangent to both given circles.

In our scipt tool we also included an animation button that traces point D as point B rotates around the big circle. This trace outlines the locus of the center of the tangent circle which is an elipse with two foci of point A and the center of the big circle.