1. Warm-Up Find the area and circumference of a circle with radius r = 4.

2. Geometry 11-1 Lines of Circles

3. Definitions

4. Example Identify each line or segment that intersects  P. chords: secant: tangent: diameter: radii: QR and ST ST PQ, PT, and PS UV ST

5. Definition

6. A common tangent is a line that is tangent to two circles.

7. Theorem 1 If a line is tangent to a circle, then it is perpendicular to the radius. A m m is perpendicular to AB B

8. Theorem 2 If two segments are tangent to a circle from the same external point, then the segments are congruent.

9. Example RS and RT are tangent to  Q. Find RS.