GEOMETRY Angles Triangles 950 8 th Math Presented

GEOMETRY Angles & Triangles 950 8 th Math Presented by Mr. Laws 450 400 x

Standard 8. G. 5 – Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles.

Essential Question What is the relationship between the sum of interior angles within a triangle compared to the sum of exterior angles on the outside of the triangle?

Target I CAN find the relationship between the sum of interior angles within a triangle. I CAN compared to the sum of exterior angles on the outside of the triangle?

Understanding Angles of a Triangle Exterior Angles Interior Angles 1. Interior angles are three angles inside of the triangle. 2. Exterior angles are all the angles that can be formed outside the triangle

Sum of Interior Angles 3. The measure sum of all interior angles within a triangle must be equal to 1800. 950 400 450 Example #1: 950 + 400 = 1800

How do I find a missing Interior Angle? Example #2 x + 900 + 600 = 1800 x + 1500 = 1800 - 1500 600 x = 300 x

How do I find a missing Interior Angle? Example # 3: Solve for x 6 x + 460 + 580 = 1800 6 x + 1080 = 1800 - 1080 -108 6 x = 720 6 6 x =12

How do I find a missing Interior/Exterior Angle? Example # 4 1000 450 x + 450 + 1000 = 1800 x + 1450 = 1800 - 1450 x = 350 x y y + 350 = 1800 - 350 y = 1450

How do I find the missing angles? Example # 5 450 x 400 950 400 x + 450 + 400 = 1800 x + 850 = 1800 - 850 x = 950 y y + 950 + 400 = 1800 y + 1350 = 1800 - 1350 y = 450 z z + 450 = 1800 - 450 z = 1350

Your Turn How do I find the missing angles? 300 250 x 250 y z

SUMMARY • What are some key concepts you should remember about this lesson? • Is there more you need to learn about this concept? • Can you answer the essential question, or do you have any more questions concerning this lesson?