1. Anna Chang T2

2. Angle-Side Relationships in Triangles The side that is opposite to the smallest angle will be always the shortest side and the side that is opposite to the largest angle will be the longest side

3. Examples Smallest to largest <B, <A, <C

4. Indirect Proof At first, you assume that the statement is false and then show that this causes a contradiction with facts Also called a proof by contradiction Writing an Indirect Proof 1. Identify the conjecture to be proven 2. Assume the opposite of the conclusion is true 3. Use direct reasoning to show that the asssumption leads to a contradiction 4. Conclude that since the assumption is false, the original conjecture must be true

5. Examples

6. p Q R

7. Triangle inequality For the sum of the length of the two shorter sides must always be longer than the third side (triangle)

8. Examples

10. Exterior angle inequality supplementary to the adjacent interior angle and it is greater than either of the non adjacent interior angles.

11. Examples

12. Hinge Theorem If the two sides of two triangles are congruent but the third side is not congruent then the triangle with the longer side will have a larger included angle.

13. Converse of Hinge Theorem If two sides of one triangle are congruent to two sides of another triangle and the third sides are not congruent, then the larger included angle is across from the longer third side.

14. Examples