1) Parallelogram ABCD 1) Given
2) AD || BC; DC || AB 2) Definition of a parallelogram (opposite sides are ||)
3) <A + <B = 180 3) Same-side interior angles are supplementary
<B + <C = 180
4) <A and <B are supplementary 4) Definition of supplementary angles
<B and <C are supplementary
Hope this helps
