9-2 Tangents

Theorem : If a line is tangent to a circle, then the line is perpendicular to the radius drawn to the point of tangency.

Corollary: Tangents to a circle from a point not on the circle are congruent.

Theorem: If a line in the plane of a circle is perpendicular to a radius at its outer endpoint, then the line is tangent to the circle.

When each side of a polygon is tangent to a circle, the polygon is said to be circumscribed about the circle, the circle is inscribed in the polygon.

Common tangent  a line that is tangent to each of 2 coplanar circles.

Common internal tangent a common tangent that intersects the segment joining the centers of the 2 circles.

Common external tangent  a common tangent that does not intersect the segment joining the centers.

A circle can also be tangent to another circle. Tangent circles are coplanar circles that are tangent to the same line at the same point.

Homework Pg. 335 1-11, 16-18