This document defines and describes triangles. It states that a triangle is a polygon with three sides and three interior angles that sum to 180 degrees. The document lists the basic parts of a triangle as sides, vertices, and angles. It then describes secondary parts such as altitudes, medians, and angle bisectors. The document classifies triangles based on side congruence as scalene, isosceles, or equilateral triangles. It also classifies triangles based on angle measures as acute, right, obtuse, or equiangular triangles.

1. TRIANGLES
MAY PAMPUAN
BUNDANG
ZAMBALES

2. Description:
• It is a polygon with the least number of
sides.
• The sum of its interior angles is 180o
.
m<1 + m<2 + m<3 = 180o
1
2 3

3. • It is named using its vertices in clockwise
or counter-clockwise manner.
A
B C
ABC
BCACBA

4. BASIC PARTS
A
B C
SIDESVERTICES ANGLES
AB
BC
AC
A
B
C
<B or <ABC
<A or <BAC
<C or <ACB

5. SECONDARY PARTS
A
B C
ALTITUDE
Is a line segment drawn perpendicularly from
one vertex to the opposite side
Also known as the height of the triangle

6. SECONDARY PARTS
Is a segment drawn from one vertex to
the midpoint of the opposite side
A
CB
MEDIAN
FE

7. SECONDARY PARTS
ANGLE BISECTOR
Is a segment drawn from one vertex to the opposite
side of the triangle
 it divides an angle of a triangle into two equal parts
F
A
B C
E
m<ABF = m<CBF
m<BAF = m<CAF
D
m<ACD = m<BCD

8. CLASSIFICATIONS
• According to the number of congruent
sides
a. Scalene – no two sides are congruent
b. Isosceles – two sides are congruent
12
8
5

9. c. Equilateral – all sides are
congruent

10. • According to the measure of its angles
a. Acute triangle – all its angles are acute
50o
65o 65o

11. b. Right triangle – with one right angle

12. c. Obtuse triangle – with at most one obtuse
angle
105o
45o
30o

13. d. Equiangular – all angles are equal
60o
60o 60o