Lesson 6.9: Interior and Exterior Angles of Triangles

Lesson 6.9

Interior and Exterior Angles of Triangles​

By Reed Carbone

Definitions:

​Interior Angles of a Triangle: The interior angles of a triangle are all of the angles on the inside of a triangle. All of these angles will sum to 180 degrees.

Exterior Angles of a Triangle: The exterior angle on a triangle is an angle on the outside (exterior) of the triangle. ​The exterior angle and interior angle will sum to 180 degrees.

Some text here about the topic of discussion

​Visuals

​What is the measure of the missing angle?

Multiple Choice

What is x?

• 71

• 120

• 109

• Not enough information

Multiple Choice

What is the measure of the missing angle?

• 40

• 90

• 50

• Not enough information

Multiple Choice

What is the missing angle?

• 61

• 180

• 90

• Not enough information

​What is the measure of the angle?

Multiple Choice

Solve for y then solve for x.

• y = 40

  x = 140

• y = 80

  x = 100

• y = 90

  x = 90

• Not enough information to solve

Multiple Choice

Solve for y

• y = 128

• y = 8

• y = 392

• I am a quitter and didn't try to solve

​Nice Trick: An exterior angle is equal to the sum of the two remote interior angles.

​Conclusion: 2 complete sentences about what you learned