1. Triangles

2. WHAT IS A TRIANGLE?

3. A triangle is: A polygon A three sided figure
A geometric shape with three angles or vertices

4. HOW CAN WE CLASSIFY THEM?
What does “classify” mean?
to sort or group together
By their angles
By their sides

5. Can be classified by their congruent sides
Triangles
Can be classified by their congruent sides

6. Scalene Triangle
no congruent sides

7. Has at least two congruent sides
Isosceles Triangle
Has at least two congruent sides

8. Has three congruent sides
Equilateral Triangle
Has three congruent sides

9. Can be classified by the measurement of their angles
Triangles
Can be classified by the measurement of their angles

10. Right Triangle
Has one right angle

11. Acute Triangle
Has three acute angles

12. Triangle with one obtuse angle
Obtuse Triangle
Triangle with one obtuse angle

13. Cut a triangle out of the sheet of paper from Mrs. Burt
Triangles
Cut a triangle out of the sheet of paper from Mrs. Burt

14. Put them together on a straight line.
Triangles
Tear off the dotted corners. Piece them together by having the corners touch.
Put them together on a straight line.

15. The sum of the angles of a triangle is ALWAYS
Triangles
The sum of the angles of a triangle is ALWAYS
180 degrees
-a straight line-

16. To find a missing angle, add up the two angles you know
Triangles
To find a missing angle, add up the two angles you know

17. ?
70˚
70˚

18. Subtract the sum from 180 and you have the missing angle
Triangles
Subtract the sum from 180 and you have the missing angle

19. 40˚ ?
70˚
70˚

20. Congruent Triangles

21. Congruent Triangles Have the same SIZE and the same SHAPE
They may be flipped or rotated

22. ABC is congruent to DEF B F E D A C

23. One for you
Name the congruent triangles remembering to name the angles in order F E Z
means “is congruent to” D
ZXY ~ FED = Y X