1. Math 8
Ms. Stewart
Unique Triangles

2. Terminology/Notation Review
Symbol
Meaning
Example
In words
Triangle
ABC
ABC has three equal sides
Angle A
Angle A is equal
to …. AB
Line Segment
The line between A and B
Congruent (same shape and size)
Triangle ABC is congruent to triangle DEF

3. What is a unique triangle?
a triangle that is one-of-a-kind
any other triangle constructed using the same specific
set of instructions will be congruent to the original triangle

4. What makes a figure congruent?
two figures are said to be congruent if they have the same shape and size
all corresponding sides are equal in length and all corresponding angles are equal in measure

5. Conditions for a Unique Triangle
All side lengths of the triangle are known (S-S-S)
When all side lengths of a triangle are known, the triangle is said to be unique.
For example: Draw a triangle with side lengths of 6 cm, 7cm and 9 cm.

6. Conditions for a Unique Triangle
The lengths of two sides and the measure of the angle between those two sides is known (S-A-S)
Example:

7. Conditions for a Unique Triangle
The measure of two angles and the length of the side between the angles (A-S-A).
Example:

8. Conditions for a Unique Triangle
The measure of two angles and the length of a side not between the angles (A-A-S)
Example:

9. Practice Question