Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Relaciones Entre Figuras Geometricas
In Spanish. Explore the world of circle interactively. Some of the topics are circumscribed and inscribed quadrilaterals and point of tangency.
Math Planet
Math Planet: Geometry: Advanced Information About Circles
Provides advanced information about circles through the use of examples and a brief video lesson. [1:00]
CK-12 Foundation
Ck 12: Geometry: Tangent Lines
[Free Registration/Login may be required to access all resource tools.] This concept teaches students about tangent lines and how to apply theorems related to tangents of circles.