# Grade 7 The Shape of Design

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Grade 7 The Shape of Design
Angles Grade 7 The Shape of Design

Recap Geometrical Terms
An exact location on a plane is called a point. Point A straight path on a plane, extending in both directions with no endpoints, is called a line. Line A part of a line that has two endpoints and thus has a definite length is called a line segment. Line segment A line segment extended indefinitely in one direction is called a ray. Ray

If we look around us, we will see angles everywhere.
Angles In Daily Life If we look around us, we will see angles everywhere.

Ray BA and BC are two non-collinear rays
What Is An Angle ? When two non-collinear rays join with a common endpoint (origin) an angle is formed. A Ray BA B Common endpoint B C Ray BC Common endpoint is called the vertex of the angle. B is the vertex of ÐABC. Ray BA and BC are two non-collinear rays Ray BA and ray BC are called the arms of ABC.

Fact: We can also think of an angle formed by rotating one
ray away from its initial position.

Naming An Angle A B C For example: ÐABC or ÐCBA
To name an angle, we name any point on one ray, then the vertex, and then any point on the other ray. A B C For example: ÐABC or ÐCBA We may also name this angle only by the single letter of the vertex, for example ÐB.

Interior And Exterior Of An Angle
An angle divides the points on the plane into three regions: Points lying on the angle (An angle) A B C P T X F R Points within the angle (Its interior portion. ) Points outside the angle (Its exterior portion. )

Measurement Of An Angle Protractor is used to measure and draw angles.
Angles are accurately measured in degrees.

There are four main types of angles.
Right angle Acute angle Obtuse angle A B C A B C A B C Straight angle B A C

Right angle: An angle whose measure is 90 degrees.
Straight Angle Right Angle Acute Angle Obtuse Angle

Examples Of Right Angle

Obtuse angle: An angle whose measure is greater than 90 degrees.
Straight Angle Right Angle Acute Angle Obtuse Angle

Examples Of Obtuse Angle

Acute angle: An angle whose measure is less than 90 degrees.
Straight Angle Right Angle Acute Angle Obtuse Angle

Examples Of Acute Angle

Straight angle: An angle whose measure is 180 degrees.
Right Angle Acute Angle Obtuse Angle

Examples Of Straight Angle

Greater than a right angle
Which of the angles below is a right angle, less than a right angle and greater than a right angle? 1. D E F 2. P Q R Test Yourself 1 Greater than a right angle A B C Right angle 3. Less than a right angle

Congruent Angles A B C D E F D E F
Two angles that have the same measure are called congruent angles. A B C 300 D E F 300 D E F 300 Congruent angles have the same size and shape.

Pairs Of Angles : Types Adjacent angles Complimentary angles
Supplementary angles Linear pairs of angles

Two angles that have a common vertex and a common ray are called adjacent angles. C D B A Common ray Common vertex D E F A B C Adjacent Angles ABD and DBC ABC and DEF are not adjacent angles Adjacent angles do not overlap each other.

ÐABC and ÐDEF are complimentary because
Complimentary Angles If the sum of two angles is 900, then they are called complimentary angles. 600 A B C 300 D E F ÐABC and ÐDEF are complimentary because ÐABC + ÐDEF = 900

ÐDEF and ÐPQR are not complimentary because
Contd…. If the sum of two angles is more than 900 or less than 900, then they not complimentary angles. 700 D E F 300 p Q R ÐDEF and ÐPQR are not complimentary because ÐDEF + ÐPQR = 1000

ÐPQR and ÐABC are supplementary, because
Supplementary Angles If the sum of two angles is 1800 then they are called supplementary angles. R Q P A B C 1000 800 ÐPQR and ÐABC are supplementary, because ÐPQR + ÐABC = 1800

ÐDEF and ÐPQR are not supplementary because
Contd…. If the sum of two angles is more than or less than 1800, then they are not supplementary angles. C B A 1100 D E F 800 ÐDEF and ÐPQR are not supplementary because ÐABC + ÐDEF = 1900

Two adjacent supplementary angles are called linear pair of angles.
1200 600 C D P ÐAPC + ÐAPD = 1800

ÐABD and ÐDBC Test Yourself 2 ÐABE and ÐDBA ÐEBA, ÐABC ÐEBD, ÐDBC
Name the adjacent angles and linear pair of angles in the given figure: Adjacent angles: C D B A E 600 300 900 C D B A E 600 300 900 ÐABD and ÐDBC ÐABE and ÐDBA Test Yourself 2 Linear pair of angles: ÐEBA, ÐABC ÐEBD, ÐDBC

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