1. 3-4 Parallel Lines and the Triangle Angle-Sum Theorem Objectives: 1) to classify triangles and find the measures of their angles 2) To use exterior angles of triangles

3. Example 1: Find the values of x, y, and z.

4. You try. Find the values of x, y, and z. 55+90+x=180 145+x=180 x=35 x+y=180 35+y=180 y=145 z+145+10=180 z+155=180 z=25

5. You can classify a triangle by its angles and sides.

6. Example 2: Classify the triangle by its sides and its angles. a) b) Try this

7. Try these. Draw and mark a triangle to fit each description. If no triangle can be drawn, write not possible and explain why. a)acute scalene b)Isosceles right c)Obtuse equiangular

8. Exterior angle of a polygon: angle formed by a side and an extension of an adjacent side Remote interior angles: the two nonadjacent interior angles

10. Example 3: Find each missing angle.

12. Try this one too.

13. Example 4: Find the value of x.

14. Try this. Find the value of x.