Tangents to a circle from a point, using Geometric Algebra

This resource is part of a series that I am preparing in support of Professor David Hestenes's goal of using Geometric Algebra(GA) to integrate high-school algebra,geometry, trigonometry,and physics into a coherent curriculum. Previous materials in this series: Dot Product: Geometric Significance and GeoGebra Coding (http://tube.geogebra.org/b/1022879#material/949399) Inner and Outer Products of Vectors Inscribed in a Circle (http://tube.geogebra.org/b/1022879#material/1015919) Geometric Algebra: Find unknown vector from two dot products (http://tube.geogebra.org/m/1481375) GeoGebra coding/usage of Geometric Algebra's wedge product (http://tube.geogebra.org/m/1503117) Resources prepared by Professor Hestenes and Robert Rowley: http://geocalc.clas.asu.edu/GA_Primer/GA_Primer/ http://geocalc.clas.asu.edu/GA_Primer/GA_Primer/introduction-to-geometric/high-school-geometry-with/index.html LinkedIn group for collaborative development of pre-university materials on GA: Pre-University Geometric Algebra https://www.linkedin.com/groups?home=&gid=8278281 Wiki for the same purpose: http://preuniversitygeometricalgebra.wikispaces.com/
Extend the problem: Given two circles, how can identify their lines of mutual internal and external tangency, using these results and ideas?