Angle Sum & Exterior Angles of Triangles

T.i.P.S.

Students should build upon their knowledge of angles including adjacent angles and supplementary angles to identify other pairs of congruent angles. Using these relationships, students can use reasoning to find the measure of missing angles. Students must understand the relationship between the measure of an exterior angle and the other two angles of a triangle.

Example

Using your prior knowledge of angles, what is the value of x in the last image?

Hint
Possible Solution

TEKS

Supporting Standard 8.8 Expressions, equations, and relationships. The student applies mathematical process standards to use one-variable equations or inequalities in problem situations. The student is expected to:
(D) use informal arguments to establish facts about the angle sum and exterior angle of triangles, the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles

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