Question

1. a b 80° 70° 1 2 d c 13. m∠1 = _ reason: _ m∠2 = _ reason: _

Explanation:

Step1: Find \(m\angle2\)

Since \(AB\parallel CD\), the exterior angle at \(B\) and \(\angle2\) are supplementary.
\(m\angle2 = 180^{\circ}- 70^{\circ}=110^{\circ}\) (Supplementary angles)

Step2: Find \(m\angle1\)

In a quadrilateral \(ABCD\) with \(AB\parallel CD\), the sum of adjacent angles is \(180^{\circ}\).
\(m\angle1=180^{\circ}-80^{\circ} = 100^{\circ}\) (Consecutive interior angles)

Answer:

\(m\angle1 = 100^{\circ}\), Reason: Consecutive interior angles are supplementary.
\(m\angle2 = 110^{\circ}\), Reason: Supplementary angles.