Q22 of 115 Page 8

Which pair of lines in fig 8.119 are parallel? Given reasons

∠A + ∠B = 115^o + 65^o

= 180^o

Therefore,

AB ‖ BC, as sum of co interior angles are supplementary.

∠B + ∠C = 65^o + 115^o

= 180^o

Therefore,

AB ‖ CD, as sum of co interior angles are supplementary.

In Fig 8.117, p is a transversal to lines m and n, ∠2 = 120° and ∠5 = 60°. Prove that m||n.

In Fig 8.118, transversal l intersects two lines m and n, ∠4= 110° and ∠7 = 65°. Is m||n?

If, l, m, n are three lines such that l||m and n⊥ l, prove that n⊥ m.

In Fig 8.120, arms BA and BC of ∠ABC are respectively parallel to arms ED and EF of ∠DEF. Prove that ∠ABC = ∠DEF.