Chapter 9 : LINES & ANGLES

Angles Parallel lines & perpendicular lines Properties of angles associated

with intersecting lines

Angles• An angle is a measure of a rotation.

• Angle above is angle AOB or < AOB

Exercise 1Name an angle below:

< ABC or < CBA

< STU or < UTS

< PQR or < RQP

• Types of angles① Acute angle less than 90o

① Right angle 90o

① Obtuse angle greater than 90o , less than 180o

② Reflex angle greater than 180o but less than 360o

Exercise 2 : Name the angle of the following diagram.

Acute angle

Obtuse angle

Right angle

Reflex angle

Obtuse angle

• Adjacent angles is an angle which is side by side.

• Sum of the adjacent angle is 180o

Example of adjacent angle

ExampleFind the sum of the following diagram:

Exercise 3

Find the value of x.

• One whole turn is 360o

• Convert angles as a fraction of a whole turn

Exercise

• Determining the sum of angles in one whole turn.

Parallel Lines & Perpendicular Lines• Parallel lines are two lines that do not meet

when the lines are extended.

Types of lin

es

• Perpendicular lines are two lines that intersect one another at a right angle.

ExerciseDetermine which of the following lines are parallel lines.

No

Yes

Yes

No

Intersecting Lines• Intersecting lines are two straight lines which

intersect if they meet at a point.• The point is known as the point of

intersection.

Types of angles

• Vertically opposite angles are equal.

• Complementary angles Is a sum of two angles equal to 90o.

• Supplementary angles Is a sum of two angles equal to 180o.

• Determining Complementary and Supplementary Angles

Exercise

SUMMARY• ANGLES

acute anglesRight anglesObtuse anglesReflex angles

• Lines Parallel linesPerpendicular lines

• Properties of intersecting lines

adjacent angles vertically opposite

anglesComplementary

anglesSupplementary

angles