2-3 Parallel lines and triangle angle sums Homework: 16-27

In this Chapter I can… 2-1: determine angle measurements from parallel lines cut by a transversal 2-2: use angle relationships to prove that lines are parallel 2-3: use interior and exterior angles of triangles to solve problems 2-4: calculate the slope of parallel and perpendicular lines

Prove the angles in a triangle add to 180 Given: AB ll DC Prove: <1+<2+<3=180° Statement Reason 1) AB ll DC 1) Given 2)<3+<4+<5=180° 2) Supplementary Angles 3) <1≅<4 3) Alt. Interior Angles 4) <2≅<5 4) Alt. Interior Angles 5) <1+<2+<3=180° 5) Substitution D C 4 5 3 1 2 A B

example x = 64 y = 74 z = 116 𝒛° Triangle Exterior Sum (Theorem)