| A | B |
|---|
| Triangle | A polygon with three sides. |
| Exterior angles | angles that form linear pairs with the interior angles of a triangle. |
| Scalene triangle |  |
| Isosceles triangle |  |
| Equilateral triangle |  |
| Acute triangle |  |
| Right triangle |  |
| Obtuse triangle |  |
| 4.1 Triangle Sum Theorem | 180 degrees,  |
| 4.2 Exterior angle theorem | the sum of the two non-adjacent interior angles,  |
| Corollary to the Triangle Sum Theorem | the acute angles of a right triangle are complementary |
| Congruent figures | when all parts of one figure are congruent to the corresponding parts of the other figure. |
| Corresponding parts | the corresponding sides and the corresponding angles of congruent figures. |
| Third angle theorem | When 2 angles of one triangle are congruent to 2 angles of another triangle, then the third angle is also congruent. |
