Topic: – 2D shapes like Circle, Triangles and Polygons

In mathematics, the concept of 2D and 3D shapes are used for explaining the different types of shapes such as triangle, circle, rectangle, quadrilateral, octagon etc. However, all the shapes which have sides are considered as the polygons. Eclipse is considered as the non-polygon as it does not have edges. Now, let us discuss some of the 2D shapes.

1.  Circle

A circle is a closed figure in which distance from the centre point is equal to the outer line, and that distance is called radius (r). A circle doesn’t have corners, it only has curved sides.

• Circle: –A circle is a 2D Shape in which locus of all points is equidistant from a central point.

Centre Point of Circle

• Radius: –Any line which is originated from the centre of the circle to any point on the circle is denoted as radius of the circle which is represented by letter “r”.Using radius of circle one can easily find out the area of a circle with the use of formula πr².

• Diameter: –The diameter of the circle is denoted by “d”.The straight line which is connected with two points of the circle through the centre point. One can use “d=2r” formula for calculation of the diameter of the circle.

2.  Triangle

It is a 3-sided polygon which has 3 edges and 3 vertices and the sum of all the 3 angles is equal to 180⁰.

3.  Square

It has 4 sides of equal length and making 90⁰ angles with each other. Moreover, diagonals of a square bisect each other at 90⁰ angles. It is also known as a 4-sided polygon and two-dimensional regular quadrilateral.

4.  Rectangle

It has 4 sides whose opposites sides are equal and parallel to each other. In a rectangle, all angles are at 90⁰.

5.  Pentagon

It is a 5 sided polygon with regular and irregular shape and has 5 diagonals. However, in a regular pentagon shape, the exterior angles are 72⁰ and interior angles are equal to 108⁰.

6.  Octagon

It is an 8 sided regular and irregular shapes. The sum of all the angles of Octagon is 1080⁰. There are 8 angles in the Octagon image.

Properties of 2D shapes

Quiz

1. A number of vertices in the square?
2. 6
3. 7
4. 4
5. 8

Answer:- 4, is the correct answer because the square has 4 points where the line meets with each other, or one can say that 4 corners.

2. Determine the shape which is shown below:-
3. Trapezium
4. Square
5. Rectangle
6. Triangle

Answer:-Triangle, is the correct answer because triangle has 3 edges and 3 vertices.

3. Determine the number of sides that a square has?
4. 3
5. 2
6. 4
7. 8

Answer:- 4, is the correct answer.

4. A number of vertices in Hexagon?
5. 8
6. 6
7. 5
8. 7

Answer:-6, is the correct answer because hexagon is a 6-sided two-dimensional shape.

5. What is the shape of an image which is shown below?
6. Pentagon
7. Rhombus
8. Circle
9. Hexagon

Answer:- Rhombus, is the correct answer because rhombus has 4 equal straight sides and its shape also looks like a diamond.

6. Which 2D shape has 3 sides?
7. Hexagon
8. Triangle
9. Pentagon
10. Octagon

Answer:-Triangle, is the correct answer because Triangle has 3 edges and 3 vertices as shown in the image below.

7. What is the diameter of a circle, if the radius of the circle is 5 inches?
8. 10 inches
9. 5 inches
10. 15 inches
11. 20 inches

Answer:- 10 inches, is the correct answer because

Radius, r = 5

The formula for calculation of diameter is, d = 2r

Therefore, d = 2 x 5 è10

8. Vertices are _____________.
9. Corners
10. Faces
11. Edges
12. Angles

Answer:-Corners, is the correct answer because vertex is the point where two points mean.

9. Name the shape having 6 vertices?
10. Pentagon
11. Rhombus
12. Octagon
13. Hexagon

Answer:-Hexagon, is the correct answer because hexagon has 6 sides.

10. Select a 2D shape from the following shape
11. Cone
12. Pentagon
13. Cube
14. Cylinder

Answer:- Pentagon, is the correct answer because Cone, Cube and Cylinder are 3D shapes.