1. Geometry
Unit 5

2. How many different triangles, if any, can be drawn with one 20° angle, one 40° angle, and one 120° angle? a. 0 triangles b. Exactly 1 triangle c. Exactly 2 triangles d. Infinitely many triangles
Similar figures - side lengths are proportional, but the angles remain the same.

3. Similar Figures Review
18 ft
10 ft

4. Standard
CC.7.G.2. Draw geometric shapes with given conditions. Focus on constructing triangles from three measures of angles or sides, noticing when the conditions determine a unique triangle, more than one triangle, or no triangle.

5. Essential Question
How do I know when conditions will form one triangle, no triangle, or more than one triangle?

7. Discovery Try to make triangles using the following colors.
5 cm, 7 cm, and 10 cm Pink, Green, Yellow
2 cm, 2 cm, 15 cm Dk green, Dk green, Blue
2 2 cm, 5 cm, 12cm Dk green, Pink, Purple
5 cm, 14 cm, and 15 cm Pink, Orange, Blue
5 cm, 5 cm, and 10 cm Pink, Pink, Yellow
What can you conclude about the side lengths of triangles?
Write down if you are able to make a triangle with the colors given.
Yes No No
Yes No
The two SHORTER SIDES must add up to be LONGER than the longest side.
Try out your conclusion with other side lengths.

9. The two SHORTER SIDES must add up to be LONGER than the longest side.
You Try… 1) 2) 4) 3)

10. The two SHORTER SIDES must add up to be LONGER than the longest side.
Task No No
Yes No
It must be longer than 2m, but shorter than 18m
It must be longer than 6 in,
but shorter than 34 in

11. Find the range of the third side of each triangle below.

12. Application of the Concept
Two miles long each because the two shorter sides must add up to be longer than the longest side and all sides must add up to be 6 miles.
It must be longer than 7 feet, but shorter than 17 feet.
The two SHORTER SIDES must add up to be LONGER than the longest side.

13. Closing
How do you know when a triangle can be formed when given various side lengths?
How do you know when and how many triangles can be formed when given three angle measurements?
Any two sides of a triangle will add up to be longer than the other side.
All angles in a triangle must add up to 180°. Triangles with the same angle measurements can have varying side lengths (similar figures).

14. Exploragons Contest

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