1. What is the Triangle Inequality Theorem?
The Triangle Inequality Theorem states that
the sum of
ANY 2 SIDES
of a triangle must be
GREATER than
the measure of the 3rd side.

2. Can multiple triangles have the same angle measures? YES!
Similar triangles are triangles whose sides are proportionate and the angles are CONGRUENT!

3. Test the Triangle Inequality Theorem
Add each pair of sides to see if it is greater than the third side.
Try it with 3 cm, 4 cm, & 6 cm
3 + 4 = 7 greater than 6
4 + 6 = 10 greater than 3
3 + 6 = 9 greater than 4
So…Since each two sums are greater than the third,
it can be a triangle.

4. Do you really have to test all 3 sides?
No.
Just add the two shortest sides.
They must be greater than the longest side.

5. Summarize our findings on pg. 90 in your book…
Let’s answer #7 together to summarize the Triangle Inequality Theorem.
Does 7, 8, and 25 make a triangle?
Is 7+8 > 25?
Summary statement: To form a triangle, the sum of any two sides must be greater than the 3rd side.

6. What is the formula for finding
area of a triangle?

7. What is the sum of all angles in any triangle?

8. Solve for missing angle measure.
Write an equation to solve for the missing angle measure.

9. Solve for the missing angle measure.
Write an equation to solve for x first.
Then you can find the missing angle measure.

10. What do you need to know about geometry?
G2 – Draw (freehand & w/ tech) geometric shapes
G2 - sum of all the angles in a triangle
G2 - how to test side lengths to see if they form a triangle.
G3 - 2D shapes that result from cross sections of right rectangular prisms & right rectangular pyramids.
G4 – area & circumference of a circle; know relationship between Area & Circum.
G5 – Angle pairs - supplementary, complementary, vertical, and adjacent angles
G6 – Solve real-world prob with area, volume, surface area of 2D & 3D objects including triangles, quadrilaterals, polygons, cubes, and right prisms.

11. Determine all the unknown measures in the figure. Handouts included.
m < M
m < x
m < y

12. Triangle Inequality Theorem
Could these be the lengths of a triangle?
4, 8, 2
5, 6, 7
6, 8, 15
7, 9, 15