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Chapter 5 Chapter 5 Properties of Circles Properties of Circles

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Page 1: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

Chapter 5Chapter 5

Properties of CirclesProperties of Circles

Page 2: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Terminology about Circle

Centre

Circumference

Chord

Radius

Diameter

Page 3: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Terminology about Circle

Minor arc Major arc

Page 4: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Terminology about Circle

Minor segment

Major segment

Page 5: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Terminology about Circle

Sector

Semi-circle

Page 6: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Properties of Chords (I)

What is the relation between AM and BM when OM AB?

Page 7: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Properties of Chords (I)

AM BM

Page 8: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Properties of Chords (II)

What is the relation between ON and OM when AB CD?

Page 9: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Properties of Chords (II)

ON OM

Page 10: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

BOCAOCCBCA ::

Arcs and Angles at the Centre

Page 11: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Arcs and Angles at the Centre

What is the relation between arcs and angles at the centre subtended by the arcs in a circle?

Page 12: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

Angles in a CircleWhat is the relation between the angle at the centre (AOB) and the angle at the circumference (ACB) subtended by the same arc?

Page 13: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

Angles in a Circle

AOB 2ACB

If AOB is a diameter, then ACB 90.

Page 14: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

Assume AB is fixed. When point C moves along the circumference of a segment, does ACB change?

Angles in a Circle

Page 15: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

ACB does not change.

i.e. angles in the same segment of a circle are equal.

Angles in a Circle

Page 16: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

Quit

Chapter 5 Properties of Circles

What is the relation between arcs and angles at the circumference subtended by the arcs in a circle?

Arcs and Angles at the Circumference

Page 17: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

Arcs and Angles at the Circumference

BDCADBCBBA ::

Page 18: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

Cyclic Quadrilaterals

What are the relations among the interior angles of a cyclic quadrilateral? Which angle equals BCE?

Page 19: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

BAD BCD 180ADC ABC 180

BCE BAD

Cyclic Quadrilaterals

Page 20: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

What is the relation between tangent PQ and radius OT?

Point of contact

Tangents to a Circle

Page 21: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

OT PQ

Tangents to a Circle

Page 22: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

TP and TQ are the tangents to the circle at P and Q respectively.

TP TQ

TOP TOQ

PTO QTO

Tangents to a Circle

Page 23: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

Angles in the Alternate Segment

If CD is the tangent to the circle at C, what is the relation between BAC and BCD?

Page 24: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

2004 Chung Tai Educational Press©

Chapter Examples

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Chapter 5 Properties of Circles

BAC BCD

Angles in the Alternate Segment

Page 25: Chapter 5 Properties of Circles. 2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 5 Properties of Circles Terminology about Circle Centre

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