1. CIRCLES RADIUS DIAMETER (CHORD) CIRCUMFERENCE ARC CHORD

2. CIRCUMFERENCE: the boundary of a circle, the length of this boundary RADIUS: a line segment that goes from the centre of a circle to its circumference; the length of this line segment DIAMETER: a line segment that runs from one side of the circle, through the centre, to the other side; the length of this line segment.

3. CHORD: a line segment that joins any two points on the circumference of a circle; the length of this line ARC: a section of the circumference of a circle that lies between two end of a chord (each chord creates two arcs); the length of this section D = 2r diameter = 2 x radius

4. Property of a Chord’s Right Bisector A chord’s right bisector passes through the centre of the circle. By drawing two random non-parallel chords and drawing the right bisector of each, the intersection of these two right bisectors is the centre of the circle.

5. ARC OF A CIRCLE- CENTRAL ANGLE A central angle is an angle whose vertex is the centre of the circle. vertex central angle and arc measure 60⁰ The central angle intercepts arc. The central angle and the intercepted arc have the same measure in degrees.

6. Circumference and Area To find circumference and area of a circle, we use the Greek letter π (pi), which is the ratio of the circumference to the diameter in all circles. The approximate value of π is 3.14 in decimal form or 3 1/7 or 22/7 in fraction form.

7. Circumference Example: Find the circumference of a circle that has a diameter of 14 metres. 14m C = πd C = (3.14)(14) C = 43.96m The circumference is 43.96 metres.

8. Area Example: Find the area of a circle with a diameter of 26 centimetres. 26cm A = πr² A = (3.14)(13)(13) A = 530.66cm²

9. Length of an Arc The length of a circle’s arc is proportional to the measure of the central angle intercepting this arc. 60⁰ Length of AB = m A0B A B Circumference 360⁰

10. Area of a Circular sector A circular sector is a region of the circle made up by the central angle and the intercepted arc. Area of sector A0B = m A0B Area of the circle 360⁰ 60⁰