1. Classifying Triangles

2. There are Two Ways to Classify Triangles
By Their Sides
By Their Angles

3. Scalene Isosceles Equilateral
If we are classifying triangles by their sides we can use the following terminology:
Scalene
Isosceles
Equilateral

4. Scalene Triangles
No sides are the same length

5. Isosceles Triangles
Two sides are the same length

6. Equilateral Triangles
All sides and angles are the same length and size.
Equilateral Triangles

7. Classifying Triangles By Their Angles
Acute
Right
Obtuse

8. Acute Triangles Acute triangles have three acute angles
This means that all angles range between 1 and 89 degrees!

9. Right Angled Triangles
Right triangles have one right angle… Who would have guessed?!?
This means that the triangle has at least one 90 degree angle. This is often shown by having a little square in the corner.

10. Obtuse Triangles Obtuse triangles have one obtuse angle
This means that there is one angle in the triangle that ranges from 91 to 179 degrees!

11. Classify this triangle.
Right Scalene

12. Classify this triangle.
Obtuse Isosceles

13. Classify this triangle.
Acute Scalene

14. Classify this triangle.
Acute Isosceles

15. Classify this triangle.
Obtuse Scalene

16. Classify this triangle.
Right Isosceles

17. The sum of the measures of any triangle is 180°.
Triangle Degrees
The sum of the measures of any triangle is 180°. x
What is the measure of x?
60°
50°

18. Triangle Degrees The sum of the measures of any triangle is 180°.
70°
What is the measure of x? x

19. Angles in a triangle sum to 180°
70°
50° x
x = 60°
Angles in a triangle sum to 180°
50° x
x = 50°
Base angles of an isosceles
triangle are equal x
x = 60°
Each angle in an equilateral triangle is 60°

20. Angles in a quadrilateral sum to 360°
50°
70° x
x = 120°
Exterior angle of a triangle equals the sum of the 2 interior opposite angles
120°
100°
80° x
x = 60°
Angles in a quadrilateral sum
to 360°

21. Types of Quadrilaterals□ I □ I I II II ^ ^ I I
Parallelogram □ □ I
Rectangle
Rhombus □ I □ I I I I II □ □ II I
Square
Trapezium
Kite