Question

Which pair of the dotted line, segments, in the following figure, are parallel. Give reason:

Answer 1

In figure,
∠1 = 45° ........(vertically opposite angles)
Lines are parallel if
∠1 + 135° = 180° .........(co-interior angles)
⇒ 45°+ 135° = 180°
⇒ 180° = 180° which is true.
Hence, the lines are parallel.