Math 9

Unit 4 – Circle Geometry

Activity 3 – Chords• Chord – a line segment that joints 2 points on

a circle. • A diameter of a circle is a chord through the

centre of a circle.

Diameter

Chord

• Perpendicular lines form a 90° angle.• Bisect – cuts a line in half so that each

side is equal.OC is perpendicular to ABOC bisects AB andcreates two equal linesegments: AC = CB

Perpendicular to Chord:

• A line segment from the centre of a circle to a chord that is perpendicular divides the chord into 2 equal lines (bisects)

radius

X

Y

In the following diagram, what is the value of angle x? what is the value of angle y?

AB

O

C

If the Length of AC is 8 cm, what is the length of AB?

The following circle has a radius of 10m. Line CD is 6 m long. How long is line AE?

The following circle has a radius of 9cm, Line BC is 14 cm long. How long is line AD?

Practice:

Practice: