Write-Up #7:
There are several interesting aspects of a circle that is tangent to two given circles. This write-up will look at how to make the a circle tangent to two given circles and the loci of the centers of the tangent circles.
Part I: Construction. This link will discuss how to do the construction and has links to some GSP sketches that have tools (scripts) for making the constructions.
Part II: Loci. This link looks at the loci of the centers of two differnt tangent circles and has links to GSP scketches of the loci.