Prepared by: Elizer S. Sampang

CONTENTSMeaning of the TriangleParts of the Triangle

- Primary Parts - Secondary Parts

Kinds of Triangle- According to Angles- According to Sides

A polygon with three sides, three angels and three vertices.

It is the union of three non collinear points.

TRIANGLE

The sum of the interior angles are 180 degrees.

TRIANGLE

Parts of theTriangle

Primary Parts

Primary PartsSides

- AB, BC, CAAngles

- A, B, C Vertices

- A, B, C

A

BC

Secondary Parts

Median- is the segment drawn from

one vertex of a triangle to the midpoint of the opposite sides.

MedianA

B CD

AD -

BD = DC

Secondary Parts

Secondary PartsAltitude

- is the perpendicular segment drawn from one vertex of the triangle to the line containing the opposite side.

Altitude - AC

Secondary PartsAngle Bisector

- is the segment drawn from one vertex and dividing the angle into two congruent angles.

Angle bisectorAP -

BAP = CAP

Kindsof

Triangle

According to

Angles

According to Angles Acute Triangle

- is a triangle with three angles are less than 90.

Examples:

50

70

60

59

5566

According to Angles Obtuse Triangle

- is a triangle with one of the angle is more than 90.

Examples:

110

2050

According to Angles Right Triangle

- is a triangle with one angle is exactly 90.

- the longest side is the hypotenuse and the two sides are the legs.

Example:

According to Angles Equiangular Triangle

- is a triangle with all angles are congruent.

60

6060

Example:

According to

Sides

According to Sides Scalene Triangle

- is a triangle with no equal sides.

Examples:

5m

7m

8m5m

3m

4m

According to Sides Isosceles Triangle

- is a triangle with two sides are congruent.

Examples:

12cm 12cm

15cm

4

4

8

According to Sides Equilateral Triangle

- is a triangle with all sides are congruent.

Example:6cm6cm

6cm

TRIANGLE

Parts Kinds

Primary Secondary

Sides Angles Vertices

Median Altitude Angle bisector

Angles Sides

Acute Obtuse Right Equiangular

Scalene Isosceles Equilateral

ACTIVITY

A. Identify the following.

1. A triangle with two equal sides.

2. A triangle whose one of its angle is more than 90 degrees.

3. A triangle whose angles are less than 90 degrees.

4. A triangle where all of its angle are congruent.

5. A triangle with no equal sides.