Shapes and angle

SHAPES AND ANGLES

1. KENDRIYA VIDYALAYA, IIT .CHENNAI-36 Class -5 th Subject- Mathematics

2. SHAPES and ANGLES Key points Polygons Types of polygons Angles Types of angles

3. A point is shown by a dot. It has no width,no length and no depth . What is a Point ? A C D B E

4. What is a line ? A line is a set of points. It can be extend in both directions. It has no end points. It has one dimension (length).

5. What is a Line segment ? A line segment is a part of the line. It has two end points. It cannot be extend A B A B Line segment

6. What is a Ray? A Ray is also a part of the line. It has one end point. It is extend from one direction.

7. An angle can be defined as the figure formed by two  rays  meeting at a common end point. What is an angle ? An angle is represented by the symbol ∠. Here, the angle below is ∠AOB.

8. Parts of an Angle Arms : The two rays joining to form an angle are called arms of an angle. Here, OA and OB are the arms of the ∠AOB. Vertex : The common end point at which the two rays meet to form an angle is called the  vertex . Here, the point O is the vertex of ∠AOB.

9. We can find angles in various things around us

10. Types of Angles Angles can be classified on the basis of their measurements as Acute Angle                      Right Angle                          Obtuse Angle Straight Angle  Reflex Angle                        Complete Angle

11. Acute Angle An angle that measures more than 0° and less than 90°. All the angles below are acute angles:

12. Right Angle A right angle is an  angle  of exactly 90 ° (degrees) The given image shows various formations of the right angle.

13. Obtuse Angle An obtuse angle is more than 90° but less than 180° All the angles below are obtuse angles :

14. Straight Angle A straight angle is an angle, whose vertex point has a value of 180 degrees. All the angles below are Straight Angle . :

15. Reflex Angle  An angle that is more than 180° but less than 360° All the angles below are Reflex Angle.

16. A full angle is an angle of one complete turn which is 360 degrees. Complete Angle

17. OPEN SHAPES CLOSED SHAPES

18. POLYGONS A polygon is any closed shape formed with three or more line segments.

19. Regular polygons All the sides and angles are equal.

20. Irregular polygon All the sides and angles are not equal.

21. How to Measure an angle ?

22. How to construct an angle ?