# Triangles by TlDmH0mc

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```									Triangles
Triangle is a polygon
with 3 sides.
Classifications for Triangles
• The angles of a triangle determine one of
its classifications.

• Acute Triangle has 3 angles less than 90
degrees each.
• Obtuse Triangle has one angle that is
greater than 90 degrees.
• Right Triangle has one angle that is
exactly 90 degrees.
The other way to classify a triangle is the
number of sides that are congruent.

Scalene Triangle has no sides congruent.

Isosceles Triangle has 2 sides congruent.

Equilateral Triangle has 3 sides congruent.
• The sum of all three angles
of any triangle is always 180
degrees.

• If you know 2 angles, you
can find the 3rd angle’s
measure by subtracting their
total from 180.
Example: 30°, 40°, & ___?
a + b + c = 180°
30 + 40 + c = 180°
70 ° + c = 180°
-70 °      -70 °
c = 110°
The angles are 30, 40, 110.
What type of triangle is it?
Obtuse Triangle
Example: 90, 20, ____?
a + b + c = 180°
90 ° + 20 ° + c = 180 °
110 ° + c ° = 180 °
-110 °       -110 °
c = 70 °
The angles are 90, 20, 70.
What type of triangle is it?
Right Triangle
Example: x, x, x
a + b + c = 180
x + x + x= 180
3x = 180
x = 60
The angles are 60, 60, 60.
What type of triangle is it?
Acute Triangle
Example: 2x, 3x, x + 30
• Find x, then find each angle.
2x + 3x + x + 30 = 180
6x + 30 = 180
─ 30 ─ 30
6x = 150
x = 25
2x , 3x ,       x + 30
50     75        55       Acute Triangle
Example:
• The sides are 3cm, 4cm, and 5cm.
• This is a Scalene Triangle.

5 cm

4 cm

3 cm
Example:
• The sides are 18 cm, 10 cm, and 10 cm.
• This is an Isosceles Triangle.

10 cm             10 cm

18 cm
Example:
• All 3 sides are 8 cm.
• This is an Equilateral Triangle.

8 cm
8 cm

8 cm
Every Triangle can be given
TWO NAMES
One for its              One for its
angles                    sides

Acute Triangle     Scalene Triangle

Obtuse Triangle    Isosceles Triangle

Right Triangle     Equilateral Triangle

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