1. 10.1 Use Properties of Tangents
Use properties of a tangent to a circle

2. Vocabulary:
A circle is the set of all points in a plane that are equidistant from a given point called the center of the circle.
A segment whose endpoints are the center and any point on the circle is a radius.
A chord is a line segment that intersects a circle in two points.
The diameter of a circle is a chord that goes through the center of the circle.

3. Vocabulary A secant is a line that intersects a circle in two points.
A tangent is a line in the plane of a circle that intersects the circle in exactly one point, the point of tangency.

4. Example 1:
Tell whether the line or segment is best described as a radius, chord, diameter, secant, or tangent of circle C. DC BD DE AE

5. Example 2

6. Coplanar Circles
Two circles can intersect in two points, one point, or no points.
Coplanar Circles that intersect in one point are called tangent circles.
Coplanar circles that have a common center are called concentric

7. Common Tangents
A line, ray, or segment that is tangent to two coplanar circles is called a common tangent.

8. Example 3: Draw common Tangents
Tell how many common tangents the circles have.

9. Theorem 10.1
In a plane, a line is tangent to a circle if and only if the line is perpendicular to a radius of the circle at its endpoint on the circle.

10. Example 4:
In the diagram, AB is a radius of circle A. Is BC tangent to circle A. Explain.

11. Example 5:
In the diagram, S is a point of tangency. Find the radius of r of circle T.

12. Theorem 10.2:
Tangent segments from a common external point are congruent

13. Example 6: Use properties of tangents.
In circle C, DA, is tangent at A and DB is tangent at B. Find x.

14.  Homework 
Pg 655/1-10,12-17,27,28,35,36