In figure 5.34 BA

Given.

BA || ED and BC || EF

Construction.

Extend ray ED and let it intersect at line BC

Theory.

⇒ If 2 lines are parallel then their corresponding angles are equal

⇒ If 2 lines are parallel then sum of their internal angles is 180°

Solution

As AB || DE

And CB is transverse

Then by corresponding angles

⇒ ∠ ABC = ∠ CDE

As CB || EF

And DE is transverse

Then by interior angles

⇒ ∠ FED + ∠ CDE = 180°

Hence ;

⇒ ∠ FED + ∠ ABC = 180°