1. Unit 2: Properties of Angles and Triangles

2. Recall When a transversal intersects two parallel lines,
The corresponding angles are equal
The alternate interior angles are equal
The alternate exterior angles are equal
The interior angles on the same side of the transversal are supplementary (add to 180°)

3. 2.3 Angle Properties in Triangles
What would be the sum of all the interior angles of a triangle?

4. Exterior angle: the angle that is formed by a side of a polygon and the extension of an adjacent side

5. Example 1 (p.87)

6. Non-adjacent interior angles: The two angles of a triangle that do not have the same vertex as an exterior angle

7. Example 2 (p.88)
Determine the relationship between an exterior angle of a triangle and its non-adjacent interior angles

8. Proof (p.88)

9. Example 3 (p.88)
Determine the measures of <NMO, <MNO and <QMO

10. Example
Determine the value of x. 

11. Example
Determine all the unknown angles.

12. Need to Know
In any triangle, the sum of the measures of the interior angles is proven to be 180°.
The measure of any exterior angle of a triangle is proven to be equal to the sum of the measures of the two non-adjacent interior angles.

13. Info for homework
What can you say about the angles of a triangle that have all equal sides? (equilateral triangle)
Then what can you say about the angles opposite of two equal sides in a triangle? (isosceles triangle)

14. Homework P
# 3,5, 7, 9, 11,13, 14, 15,