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Section 9-2. Tangents. Theorem 9-1. If a line is tangent to a circle, then the line is perpendicular to the radius drawn to the point of tangency. Point of Tangency. P. Corollary. Tangents to a circle from a common point are congruent. A. B. Theorem 9-2.
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Section 9-2 Tangents
Theorem 9-1 • If a line is tangent to a circle, then the line is perpendicular to the radius drawn to the point of tangency.
P Corollary • Tangents to a circle from a common point are congruent A B
Theorem 9-2 • If a line in the plane of a circle is perpendicular to the 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 and the circle is inscribed in the polygon.
Common tangent • A line that is tangent to each of two coplanar circles
A B Common internal tangent • Intersects the segment joining the centers
B A Common external tangent • Does not intersect the segment joining the centers.
Tangent circles • Coplanar circles that are tangent to the same line at the same point
Externally Tangent l A B
Internally Tangent l D C