Answer:
adbe
Step-by-step explanation:
because BC//AD
=> ∠BCA = ∠CAD
ΔABC has: ∠B + ∠BCA + ∠BAC = 180°
ΔADC has : ∠D + ∠CAD + ∠ACD = 180°
but ∠B = ∠D; ∠BCA = ∠CAD
=> ∠ BAC = ∠ACD
=> AB // DC
ABCD has AB//DC, BC//AD
=> ABCD is a parallelogram
=> AB ≅ CD
