Step-by-step explanation:
1. AB ⊥ BC, DE ⊥ EF, AB ≅ DE, BC || FE
Given
2. ∠ACB ≅ ∠DFE
Alternate interior angles
3. ΔABC ~ ΔDEF
AA similarity
4. AB / DE = BC / EF
Similar triangles
5. 1 = BC / EF
Definition of congruency
6. BC = EF
Algebra
7. BC ≅ EF
Definition of congruency
