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Mathematics
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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