Question

In the given figure, BA PARALLEL TO ED AND BC PARALLEL TO EF. SHOW THAT ANGLE ABC + ANGLE DEF =180 DEGREE

Answer 1

If line FE is extended to join line AB at point G, angle FGB and angle ABC become supplementary angles because BC||EF = BC||GF.
= angle FGB + angle ABC = 180°
angle FGB = angle DEF since DE||AB and joined by line EG.
Therefore, angle DEF + angle ABC = 180°.