Geometry
Angles In Shape
 Every object around us has a specific shape.
 The shape is classified into two types: Open shape and Closed shape.
 The shape in which the starting and the ending point are not the same is called the open shape. An open shape has space between them.

The shape in which the starting and the ending point are the same is
called the closed shape. A closed shape has no space
between them.
 A circle is a closed shape.
 A semicircle is an open shape.
 The angle inside the shape is called the interior angle of a shape.
Angles in a Triangle
 A triangle is three sides bounded figure.
 It has three interior angles.
 Sum of the interior angle of the triangle is 180°.
The threeinterior angle of the triangle is ∠A, ∠B, and ∠C. ∠A + ∠B + ∠C = 180°.
Equilateral angle:
A triangle in which all the interior angles are equal to 60° is called an equilateral triangle.
Isosceles angle:
A triangle in which two interior angles are equal is called an isosceles triangle.
Scalene triangle:
A triangle in which no interior angles are equal is called a scalene triangle.
Rightangled triangle:
A triangle in which one of the angles is equal to 90° is called a rightangled triangle.
Angles in a Rectangle
 A rectangle is four sides closed figure.
 Opposite sides of the rectangle are parallel and equal.
 It has 4 interior angles.
 Each interior of the rectangle is equal to 90°.
 Sum of the interior angle of the rectangle is 360°.
The fourinterior angle of the rectangle is ∠A, ∠B, ∠C, and ∠D.
∠A = ∠B = ∠C = ∠D = 90°
∠A + ∠B + ∠C + ∠D = 360°
Angles in a Square
 A square is four sides closed figure.
 Each side of the square is equal in length.
 It has 4 interior angles.
 Each interior of the square is equal to 90°.
 Sum of the interior angle of the square is 360°.
The fourinterior angles of the square are ∠A, ∠B, ∠C, and ∠D.
∠A = ∠B = ∠C = ∠D = 90°
∠A + ∠B + ∠C + ∠D = 360°
Missing angles
Example 1:
Find the missing angle of the given triangle.
Solution:
Sum of the given angle = 120° + 28°
= 148°
The total sum of the interior angle = 180°
Missing angle = 180° – 148°
= 32°
Example 2:
Find the missing angle.
Solution:
Given angle = 60°
Total sum = 90°
Missing angle = 90° – 60°
= 30°
Did you know?