Classifying triangles

2. Why is the
Obtuse triangle
always upset?
Because it is
never Right like
you.

3. A triangle is a polygon with:
three sides,
three vertices and
three angles.
A Triangle

4. A triangle can be classified by its sides and/or its
angles.
By its sides:
All three sides are equal.
Equilateral Triangle

5. Two sides are equal.
Isosceles Triangle.

6. None of the sides are equal
Scalene Triangle

7. By its Angles.
Acute angle
Acute triangle
In an acute triangle as the name
implies, all angles are acute angles.

8. Obtuse angle
Obtuse triangle
In an obtuse triangle, one
angle is obtuse, while the
other two are acute.

9. Right angle
Right triangle
A right triangle has one
right angle and two acute
angles.

10. The sum of the angles in a triangle is always 180ᵒ
<A + <B + <C = 180ᵒ
60ᵒ + 60ᵒ + 60ᵒ = 180ᵒ

11. 72ᵒ + 72ᵒ + 36ᵒ = 180ᵒ 60ᵒ + 30ᵒ + 90ᵒ = 180ᵒ
Find the sum of the angles.
Find the missing angle.
34ᵒ + 120ᵒ + <C = 180ᵒ
<C = 180ᵒ - (34ᵒ + 120ᵒ )
<C = 180ᵒ - 154ᵒ = 26ᵒ
26ᵒ
30ᵒ + 70ᵒ + angle = 180ᵒ
angle = 180ᵒ - (30ᵒ + 70ᵒ )
angle = 180ᵒ - 100ᵒ = 80ᵒ
80ᵒ

12. Find the missing angles, and classify the triangles by their angles.