Triangles

1
Triangles

• by
• Deb Kiley
• Butch Fitzgerald
• Sandymount Elementary School
• February 2005

2
First, Know Your Angles

• Acute less than 90 degrees
• Right exactly 90 degrees
• Obtuse greater than 90 degrees
• Straight exactly 180 degrees

3
Acute

• Less than 90 degrees

vertex
4
Right

• Exactly 90 degrees

vertex
The intersection of the rays are perpendicular.
5
Obtuse

• Greater than 90 degrees

vertex
6
Straight

• Exactly 180 degrees

7
Triangles

• 3 sided polygon
• Identified by angles and sides
• The sum of all angles equals 180 degrees

8
Types of Triangles

• By angles
• Acute
• Right
• Obtuse
• By sides
• Equilateral
• Isosceles
• Scalene

9
Acute Triangle

• A third line segment connecting the two rays of
  an angle makes an acute triangle.

Acute triangles have 3 acute angles.
10
Right Triangle

• A third line segment connecting the two rays of
  an angle makes a right triangle.

Right triangles have 1 right angle and 2 acute
angles.
11
Obtuse Triangle

• A third line segment connecting the two rays of
  an angle makes an obtuse triangle.

Obtuse triangles have 1 obtuse angle and 2 acute
angles.
12
Equilateral Triangle

• A third line segment connecting the two rays of
  an angle makes an equilateral triangle.

Equilateral triangles have 3 congruent sides.
13
Isosceles Triangle

• A third line segment connecting the two rays of
  an angle makes an isosceles triangle.

Isosceles triangles have only 2 congruent sides.
14
Scalene Triangle

• A third line segment connecting the two rays of
  an angle makes a scalene triangle.

Scalene triangles have NO congruent sides.
15
Straight Triangle

• ?

BCR
16
Triangle to Trapezoid

• A trapezoid has only 1 set of parallel sides. It
  can be made by cutting a triangle in half.

trapezoid