The document provides definitions and characteristics of different types of triangles based on their sides (scalene, isosceles, equilateral) and angles (acute, right, obtuse). It explains that a triangle has six parts, including three sides and three angles, and presents fundamental properties such as the sum of angles equaling 180 degrees and specific properties pertaining to isosceles triangles. Additionally, it emphasizes the relationship between various triangle types and their respective definitions.

1. Angles and Triangles
Presented By,
Krishna kumari
and Z,verghese
KendriyaVidyalaya,
I N S Hamla.

2. Contents

4. Scalene Triangles
• Definition: A triangle,no two of whose sides are equal, is called a scalene
triangle. E.g..
A
B
C

6. Isosceles Triangle
Definition: A triangle, two of whose sides are equal, is called an isosceles
triangle.e.g.
A
B C

7. Equilateral Triangle
• Definition: a triangle whose all sides are equal, is called an
equilateral triangle.e.g.
A
B C

8. Acute triangle
• Definition:A triangle each of whose angles is acute is called an acute angled
triangle or simply acute triangle.e.g.
A
B C

10. Right Triangle
• Definition: A triangle with one angle a right angle is called a right angled
triangle or simply right triangle.e.g.
A
B C

11. Obtuse triangle
• Definition: A triangle with one angle an obtuse angle is known as obtuse
angled triangle or simply obtuse triangle.e.g.
A
B C

13. Triangles-Introduction
• Definition: A plane figure bound by three lines in a plane is called a
triangle.a triangle has 6 parts.(3sides & 3angles).
• Here,AB,AC&BC are the sides,A,B & C are points.
A
B C

14. Types Of Triangles
On the basis of sides:
1. Scalene triangles
2. Isosceles triangles
3. Equilateral triangles.
On the basis of angles:
4.Acute triangles
5.Right triangles
6.Obtuse triangles.
An equilateral triangle is an isosceles triangle but the converse
is not true.

15. Scalene Triangles
• Definition: A triangle,no two of whose sides are equal, is called a scalene
triangle. E.g..
A
B
C

16. Isosceles Triangle
Definition: A triangle, two of whose sides are equal, is called an isosceles
triangle.e.g.
A
B C

17. Equilateral Triangle
• Definition: a triangle whose all sides are equal, is called an
equilateral triangle.e.g.
A
B C

18. Acute triangle
• Definition:A triangle each of whose angles is acute is called an acute angled
triangle or simply acute triangle.e.g.
A
B C

19. Right Triangle
• Definition: A triangle with one angle a right angle is called a right angled
triangle or simply right triangle.e.g.
A
B C

20. Obtuse triangle
• Definition: A triangle with one angle an obtuse angle is known as obtuse
angled triangle or simply obtuse triangle.e.g.
A
B C

21. Triangle properties-1
• Property 1:the sum of the three angles in a triangle is 180 degrees.
• Property 2:if a side of a triangle is produced then the exterior angle so
formed is equal to the sum of the two interior opposite angles.
A
B C
Here, angle A+angle
B+angle C=180 degrees.
A
B C
D
Here,angle ACD = angle
A+angle B

22. Triangle Properties:Isosceles
• Property1: the angles opposite to equal sides are equal.
• Converse: the sides opposite to equal angles are equal.
A
B C
P
Q R