Question

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

Answer 1

∠1 + 100°= 180°

⇒∠1 = 180°− 100°= 80° ......... (linear pair)

Lines 1 and 2 will be parallel If ∠1 = 70°

⇒ 80° = 70° which is not true.

∴ ∠1 and ∠2 are not parallel.

∠3 and ∠5 will be parallel If 80° = 70° are corresponding angle which is not true.

∴ ∠3 and ∠5 are not parallel.

But ∠1 = 80° ........ (alternate angles)

⇒ 80° = 80° Which is true.

∴ ∠2 and ∠4 are parallel.