1. Tangents November 21, 2008

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

3. More about properties of tangents Corollary: Tangents to a circle from a point are congruent.

4. Even more about properties of tangents 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.

5. Inscribed and circumscribed, revisted You can also inscribe a circle.

6. Internal tangent A common internal tangent intersects the segment joining the centers.

7. External tangent An external tangent does not intersect the segment joining the centers.

8. Internal or External?

9. Find the values

10. Circumference Circumference is the measurement of the distance around the edge of a circle. Also known as 'periphery', 'perimeter'. The formula is C= πd or C= π(2r)