The document discusses properties of tangents to circles. It states that a line tangent to a circle is perpendicular to the radius drawn to the point of tangency. It also notes that if two segments are drawn from the same exterior point to tangents of a circle, the segments are congruent. Additionally, if a line is perpendicular to a radius at its endpoint on a circle, then the line is tangent to the circle. The document defines externally tangent circles as those that intersect at one point and internally tangent circles as those that intersect at one point. It describes a common tangent as a line tangent to two circles, being either external and not cutting through the line connecting circle centers, or internal and cutting through that line.

1. 9-2 Tangents

5. Tangent Circles Two circles that intersect at one point. Externally Tangent

6. Tangent Circles Two circles that intersect at one point. Internally Tangent