Geometry and Shapes

Geometry is useful in recognizing the shapes. Do you want to know the shape of` your house, toys and favorite chocolate?

Let Us Revise Few Shapes

Now we will study the shapes formed with the help of sleeping lines, slanting lines, curved lines!

Angles

Angle is the figure formed by two rays, called sides of angle. Both sides have common end point, called vertex of the angle.

• A positive angle goes anti-clockwise.
• A negative angle goes clockwise.

Type of Angles

 Sr No Angle Type Description 1 Acute Angle An angle less than 90° 2 Right Angle An angle that is equal to 90° 3 Obtuse Angle An angle greater than 90° but less than 180° 4 Straight Angle An angle equals to 180° 5 Reflex Angle An angle greater than 180°

Circles

A circle is the locus of all the points that are equidistant from central point.

• Radius of Circle: It is the distance from the center to the edge.

• Diameter: It starts from one end of the circle and ends on another while going through center.

• Circumference: It is the distance around the edge of circle.

• Area of Circle: The area of circle is Π times the radius squared.

Example 1: A circle has radius 50 cm. Calculate its circumference.

Sol: Diameter = 2×50 = 100 cm

Circumference = Π×100 = 314 cm

Example 2: Find the area of circle having radius 2 m?

Sol: Area = Π×R² = 3.14×2×2 = 3.14×4 = 12.56 m²

Practice These Questions

• Find out the number of sleeping lines, slanting lines, curved lines, circles, square, triangle and rectangle in the figure below:

• Name the angles:
1. 78°
2. 156°
• 45°
1. 255°
2. 180°

• Find out the diameter, circumference and area of circle whose radius is 20 cm?

Recap

• Ray is extended to one end only.
• Line is extended towards both ends.
• Line segment is a part of line with two end points.
• Angle less than 90° is acute angle; angle more than 90° is obtuse angle.
• 90°angle is called right angle.
• Radius of circle is half of its diameter.