Triangles and Types of Triangles

Sub. :- Mathematics

Std. :- 6th

Chapter no. 20

S

TD

L

M N

DE

FName of the triangle

Name if its vertices

Name of its three sides

Name of its angels

STD

A

N

L

.

..U

M

.

..P

.Q

OS

BC

.D

. Name of the triangle

Interior points

Points on triangle Exterior Points

An exterior angle of a triangle X

Y zW

.

An angle that forms a linear pair with an angle of a triangle is called an exterior angle of the triangle .

Different Types of Triangles• There are several different types of

triangles. • You can classify a triangle by its sides and

its angles.• There are THREE different classifications

for triangles based on their sides.• There are FOUR different classifications

for triangles based on their angles.

Classifying Triangles by Their Sides• EQUILATERAL – 3 congruent sides

• ISOSCELES – at least two sides

congruent

• SCALENE – no sides congruent

EQUILATERAL

ISOSCELES

SCALENE

Classifying Triangles by Their Angles

• ACUTE – all angles are acute

• RIGHT – one right angle

• OBTUSE – one obtuse angle

ACUTE

RIGHT

OBTUSE

If all angles of a triangle are acute then the triangle is called acute angled triangle.

An acute angled triangle.

Can You Classify the Different Triangles in the Picture Below?

Classify the following triangles: AED, ABC, ACD, ACE

The Classifications…• Triangle AED = Equilateral• Triangle ABC = Equilateral• Triangle ACD = Isosceles, Obtuse• Triangle ACE = Scalene, Right