Mathematics (2019) Grade(s): 8

MA19.8.25

Analyze and apply properties of parallel lines cut by a transversal to determine missing angle measures.

Unpacked Content

Knowledge

Students know:
  • That a straight angle is 180 degrees
  • That a triangle has three interior angles whose sum is 180 degrees.
  • The definition of transversal.
  • How to write and solve two-step equations.

Skills

Students are able to:
  • Make conjectures about the relationships and measurements of the angles created when two parallel lines are cut by a transversal.
  • Informally prove that the sum of any triangle's interior angles will have the same measure as a straight angle.

Understanding

Students understand that:
  • Missing angle measurements can be found when given just one angle measurement along a transversal cutting through parallel lines.
  • Every exterior angle is supplementary to its adjacent interior angle.
  • Parallel lines cut by a transversal will yield specific angle relationships that are connected to the concepts of rigid transformations (i.e. vertical angles are reflections over a point. corresponding angles can be viewed as translations).
  • The sum of the interior angles of a triangle is 180 degrees.

Vocabulary

  • Transversal
  • Corresponding Angles
  • Vertical Angles
  • Alternate Interior Angles
  • Alternate Interior Angles
  • Supplementary
  • Adjacent
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