Tangents of Circles

Internal vs External Common Tangents

This video covers the situation where you have two circles and you're supposed to classify them. If the circles themselves are tangent, they can be "internally" or "externally" tangent. More common is that a segment is tangent to both circles, and you're supposed to know if that "common tangent" is internal or external.

Tangent Theorems

This video is a quick summary of the theorems you should know for tangents to circles, whether you're working problems or looking for hints for your next proof.

Circle Tangent Problems

This is a long video because there's a lot of ground to cover! I work all the most common types of questions, involving both the fact that tangents are perpendicular to the radius they intersect as well as problems where you have to solve for the length of tangents.

Tangents & Inscribed Angles

This is a short video, but it's an important one that addresses the hardest-to-spot tangent problems: the ones where they give you the length of an arc. If you're not on the lookout, you won't realize that arc is inscribed by an angle where one side is a tangent to the circle!

Tangent Proofs

First off we'll review the theorems for tangents, then we'll prove the one about how tangents from a single point are congruent. Hint: congruent triangles are involved.