(i) Given, a||b, then ∠1 = ∠5 [Corresponding angles]
If two parallel lines are cut by a transversal, each pair of corresponding
angles are equal in measure.
(ii) Given, ∠4 = ∠6, then a||b [Alternate interior angles]
When a transversal cuts two lines such that pairs of alternate interior
angles are equal, the lines have to be parallel.
(iii) Given, ∠4 + ∠5 = 180°, then a||b [Co-interior Angles]
When a transversal cuts two lines, such that pairs of interior angles on the
same side of transversal are supplementary, the lines have to be parallel.

Class 7 Maths Chapter 5 Exercise 5.2

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