An angle is formed when two straight lines meet at a common point. This common point is called the vertex of the angle. The two lines are called the sides of the angle. An angle is usually represented by English alphabets. In the picture below, B is the vertex, AB and BC are the sides, and the angle formed at the vertex is called angle ABC.
Look at the picture
A-B=side
B=vertex
B-C=side
ABC is an angle
A.How to measure Angle??
Step 1: Place the protractor so that the center of the protractor is aligned with the vertex. The base of the protactor must be aligned with one of the sides of the angle.
Step 2: To measure the inner angle, read the number on the inner scale (counter-clockwise). To measure the outer angle, read the outer scale (clockwise). The number at the point where the other side of the angle (not the one aligned with the base) and the protractor scale meet, is the degree of the angle.
Step 2: To measure the inner angle, read the number on the inner scale (counter-clockwise). To measure the outer angle, read the outer scale (clockwise). The number at the point where the other side of the angle (not the one aligned with the base) and the protractor scale meet, is the degree of the angle.
B.Type of Angles
1.Acute Angle
2.Right Angle
3.Obtuse Angle
4.Straight Angle
1.Acute Angle
An angle that is more than 0o and less than 90o is called an acute angle.
HOW to REMEMBER
Acute means pointed or sharp. It is narrow. One must bend forward to sit in an acute angled chair.
2.Right Angle
An angle that is exactly 90o is called a right angle.
HOW to REMEMBER
Look at picture :
3.Obtuse Angle
An angle that is more than 90o and less than 180o is called an obtuse angle.
HOW to REMEMBER:
4.Straight Angle
An angle that is exactly 180o is called an straight angle.
HOW to REMEMBER
Reference:http://www.ezschool.com
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