Triangles can be classified in several ways. They have three sides and three angles. Triangles are classified based on the length of sides into equilateral, isosceles, and scalene triangles. They are also classified based on angle magnitude into acute, right, and obtuse triangles. The interior is the region within the triangle boundary, while the exterior is outside the boundary. An equiangular triangle has three equal angles and is also equilateral.

1. TRIANGLES
Presented by:
Ann Treesa Sebastian

2. • Triangles – Basic concepts
• Regions – Interior, Exterior,Triangular
• Types of triangles
• Based on length of sides
• Based on the magnitude of the angles
• Equiangular triangles

3.  A triangle is a closed figure made of three line segments.
 It has three vertices, three sides and three angles.
 The line segments forming a triangle are the three sides of
the triangle.
 The point where any two of the three line segments of
a triangle intersect is called the vertex of the triangle.
 When two line segments intersect, they form an angle.
 A triangle is denoted by
A
B
C

4. o The region within the boundary of a
triangle is called the interior region of
the triangle.
o Points P, Q, S and R are in the interior of
∆ ABC.
o The region outside the boundary of a
triangle is called the exterior region of
the triangle.
o Points X, Y and Z are in the exterior of
∆ ABC.
o Points E, F and H are in the boundary of
∆ ABC.
o The interior region along with the
boundary is known as the triangular
region.

5. A triangle has three sides and three angles. Triangles can be
classified into different categories based on:
• the length of the sides
• the magnitude of the angles

6. Based on the length of the sides triangles are classified into the
following categories:
 Equilateral triangles
 Isoscles triangles
 Scalene triangles

7. When all the three sides of a triangle are equal it is
called an equilateral triangle.

8. If two sides of a triangle are equal in length, then it is
called an isosceles triangle.

9. A triangle having no two sides equal is called a scalene
triangle. That is all three sides have different length.

10. Based on the length of the sides triangles are classified into the following
categories:
 Acute - angled triangles
 Right - angled triangles
 Obtuse - angled triangles

11. If each of the three angles of a triangle are acute, that is
less than 90 degree, it is called an acute angled triangle or
simply an acute triangle.

12. When one angle of a triangle is a right angle, that is
90 degree, the triangle is called a right angled triangle
or simply a right triangle

13. When one angle of a triangle is a right angle, that is
greater than 90 degree, the triangle is called an obtuse
angled triangle or simply an obtuse triangle

14. When the three angles of a triangle are equal, the triangle is
known as equiangular triangle. An equiangular triangle is also
equilateral.