Three coplanar lines ,

MATHEMATICS · Subjective · GCSE · Mathematics · Geometry and Measures · Geometry and Measures

Problem

Three coplanar lines

a

b

, and

c

are intersected in that order by the same transversal

t

at points

D

E

, and

F

. The interior angle between

a

and

t

D

on the left of

t

equals the interior angle between

c

and

t

F

on the right of

t

. Which two of the lines

a

b

c

must be parallel? Give a reason for your answer.