1. 8.2: Properties of a Chord Circle Geometry

2. What is a chord?  a chord is line segment joining two endpoints that lie on a circle.

3. What is a chord?  A circle can have many chords but there is one special chord left to mention

4. What is a chord?  It turns out that a diameter of a circle is the longest chord of this circle since it passes through the center. A diameter satisfies the definition of a chord, however, a chord is not necessarily a diameter.  Therefore, every diameter is a chord, but not every chord is a diameter.

5. Working with Chords, Radii and Diameters http://www.mathgoodies.com/lessons/vol2/geometry.html

6. Chord Property #1, #2 and #3  A perpendicular line from the centre of a chord to the centre of a circle: #1: Makes a 90° angle with the chord #2: Creates two equal line segments RS and QR #3: Must pass through the centre of the circle O

7. Chord Property #1, #2 and #3  Let’s play with this….  http://staff.argyll.epsb.ca/jreed/math20p/circles /chordBisector.htm http://staff.argyll.epsb.ca/jreed/math20p/circles /chordBisector.htm  http://www.mathwarehouse.com/geometry/circ le/chord-perpendicular-bisector.html http://www.mathwarehouse.com/geometry/circ le/chord-perpendicular-bisector.html

8. Let’s get crazy… b 3 8 12 Find b.

9. Let’s get crazy… b 3 8 12 Step 1: What do we need to find? We need a radius to complete this big triangle. Find b.

10. Let’s get crazy… b 3 8 12 Find b. How do we find a radius? We can draw multiple radii (radiuses).

11. Let’s get crazy… b 3 8 12 Find b. How do we find a radius? Now what do we have and what will we do?

12. Let’s get crazy… b 3 8 12 Find b. How do we find a radius? We create this triangle but how do we get the missing side?

13. Let’s get crazy… b 3 8 12 Find b. How do we find a radius? We create this triangle but how do we get the missing side? 4

14. Let’s get crazy… b 3 4 12 Find b. !!!Pythagorean Theorem!!! a 2 +b 2 =c 2 so 5 2 +12 2 =169 so b is 13. 5 5 13

15. Assignment Time  Pg. 397-340 3, 4, 5, 6, 7, 10, 11, 18, 19(Draw it out!)