Question 255370
I would have mentioned parallel lines intersected by a transversal forms angles which are congruent.
We have line AC intersecting BE and CD
and line AD intersecting lines BE and CD
Since (given) BE is parallel to CD, then angles ABE and ACD are congruent and angles AEB and ADC are congruent.
triangles CAD and BAE share angle BAE all three angles are congruent .
Since all three angles are congruent the triangles are similar.
since the triangles are similar their corresponding sides are proportional
therefore    blah blah QED

PS you didn't say where angle 1 and angle 3 are