Exterior angles of a triangle plus unknown angle problems (8th grade math)
If we extend the sides of a triangle, we find the exterior angles of a triangle. Since each exterior angle is supplementary to one of the angles of the triangle, it is easy to find their angle measure (if you know the angle in the triangle).
After explaining this term, I show you two different unknown angle problems that you can solve yourself -- or watch me solve them, using basic principles such as the fact corresponding angles and vertical angles are congruent.
See also
Angle sum of a triangle — video lesson
Math Mammoth Grade 8 curriculum
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