Triangles…
SOL5.12b
GES
Mrs. Norman
CLASSIFYING
TRIANGLES
CLASSIFYING TRIANGLES
 Why do we classify triangles?
 Artists and architects often use triangular elements in their designs.
 Classifying triangles makes it easier to describe them.
CLASSIFYING TRIANGLES
How can these triangles be
classified?
One way is:
By the length of their sides.
4
4
4
5
7
5
9
2
8
CLASSIFYING TRIANGLES
Equilateral triangle
 All sides are the same (equal) length.
The sum total of every triangle = 180°
So, if all of the angles are the same…
3 ÷ 180° = 60°
Each of the three angles of an
equilateral triangle is 60°
CLASSIFYING TRIANGLES
Isosceles triangle
 At least two sides are the same (equal) length.
4
4
6
4
4
CLASSIFYING TRIANGLES
Scalene triangle
 No sides are the same (equal) length.
9
2
7
9
2
7
CLASSIFYING TRIANGLES
Another way you can classify
triangles is:
by the measure of their angles
CLASSIFYING TRIANGLES
Right triangle
 One angle is a right (90°) angle.
 The sides have special names.
 The legs are the two sides that form a right triangle
 The third side is the hypotenuse
hypotenuse
legs
legs
hypotenuse
CLASSIFYING TRIANGLES
Acute triangle
 All three angles are acute angles.
CLASSIFYING TRIANGLES
Obtuse triangle
 One angle is an obtuse angle.
CLASSIFY TRIANGLES
Isosceles:
Acute:
2 congruent sides
all angles are
acute
Scalene:
Obtuse:
each side a
different length
has an obtuse
angle
Equilateral:
all 3 sides
congruent
Right:
has a right
angle
Image from math.com
Now You know all
about Triangles…
So lets practice!
CLASSIFYING
TRIANGLES
BY SIDES AND ANGLES
http://www.ixl.com/math/grade-4/classify-triangles-by-side-lengths
http://www.ixl.com/math/grade-4/classify-triangles-by-angles
http://www.ixl.com/math/grade-7/classify-triangles
DIRECTIONS:
 When the slide appears, say BOTH NAMES for the type of
triangle aloud before the computer shows you the answer.
 Classify each triangle by both its SIDES and its ANGLES.
 You will have 6 seconds.
Classify by sides:
Classify by angles:
Classify by sides:
also
Isosceles
Triangle
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Classify by sides:
Classify by angles:
Are you a
triangle
expert?