1. Bell Work
Find the measure of the missing variables and state what type of angle relationship they have(alt. interior, alt. ext, same side interior, corresponding).
1) 2)
3) 4)

2. Outcomes I will be able to:
1) Classify a triangle by its sides and/or angles
2) Find the measure of interior angles of a triangle using the Triangle Sum Theorem
3) Find the exterior angles of a triangle using the Exterior Angle Theorem

3. Tablet Activity Download the Geometry Pad app from the Playstore.
Do not download anything other than Geometry Pad, as this will slow down the download!!!
Set your tablet aside, we will use it later!!!

4. Triangles What is a triangle?
Triangle – A polygon formed by three segments joining three noncollinear points
Example:
There are two ways to classify triangle:
1) By its sides
2) By its angles

5. Names Of Triangles Classifications By Sides
1. Equilateral Triangles
Example:
What does it mean for a triangle to be equilateral?
***All sides must be congruent

6. Names of Triangles Classifications by Sides
2. Isosceles Triangle
Example:
What does it mean for a triangle to be isosceles?
***At least two sides are congruent
***So, an equilateral triangle is also isosceles

7. Names of Triangles Classification by Sides
3. Scalene Triangle
Example:
What does it mean for a triangle to be scalene?
***No sides are congruent

8. Classify the following Triangles1) 2) 3) 4) 5) 6)

9. Names of Triangles Classification by Angles
4. Acute Triangle
Example:
What do you notice about all of the angles?
***An acute triangle has all acute angles

10. Names of Triangle Classifications by Angles
5. Equiangular Triangle
Example:
What do you notice about all of the angles?
They are all congruent
***An equiangular triangle has all angles congruent
***An equiangular triangle is also acute.

11. Names of Triangles Classification by Angles
6. Right Triangle
Example:
What do you notice about the angles?
There is one right angle
***There is one right angle in every right triangle

12. Names of Triangles Classification by Angles
7. Obtuse Triangles
Example:
What do you notice about the angles?
***There is one obtuse angle in every obtuse triangle

13. Classifying Triangles
When classifying triangles, we can classify them by both their sides and their angles
What type of triangle would
this be?
Right Isosceles Triangle or
Isosceles Right Triangle
We can name a triangle by
angles or sides first

14. Classifying Triangles Examples
How would you classify this triangle?
Obtuse Scalene Triangle

15. Classifying Triangle Examples
How would you classify this triangle?
Acute Scalene Triangle

16. Parts of Triangles Vertex – Each point joining the sides of a triangle
Example:
A, B, and C are all vertices
Adjacent Sides – The two sides sharing a vertex
AC and AB, AB and BC, AC and BC are adjacent sides A B C

17. Parts of Triangles The sides that form the right angle
hypotenuse
AB and BC are the legs of this triangle
leg
The side opposite the right
angle
leg C B

18. Tablet Activity
Plot the points from each problem and classify the triangles by looking at the measurements of their sides and angles
See the overhead on how to use the app and the answers for #1!!!

19. Parts of Triangles The non-congruent side of an isosceles triangle
leg
The non-congruent side of an
isosceles triangle
base
The congruent sides of an
isosceles triangle
leg

20. Types of Angles in Triangles
There are both interior and exterior angles we are concerned with when looking at triangles
Interior angle are inside the triangle
Exterior angles are outside the triangle

21. Triangle Sum We can conclude that all the angles add to 180°
Think about the angle
sums!!!
We can conclude that all the angles add to 180° 67 50 43 90 40 70

22. Triangle Sum Theorem

23. Exterior Angle Theorem
We can conclude that the sum of the remote interior angle is equal to the exterior angle 60 80 90 40
Compare the inside angles
to the outside angle
=120 30

24. Exterior Angle Theorem

25. Examples How can we solve this? 42 + 90 + x = 180 132 + x = 180
x = 48

26. Examples How can we solve this? x+ 110 = 4x – 7 -x -x 110 = 3x – 7
117 = 3x
39 = x

27. Examples How can we solve this?
Remember, we can label things we know even if they are not in our picture.
Now we have,
33 + x + 90 = 180
123 + x = 180
x = 57 90

28. Examples How can we solve this? x + x + 30 = 180 2x + 30 = 180
2x = 150
x = 75

29. Independent Practice 1) Solve for the missing variable
2) Circle the chart
r = 180
r + 90 = 180
r = 90