∠∠D =∠DBE (known)

∴BE∥CD (the inner angles are equal and the two straight lines are parallel)

∴∠ Abe =∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠∠

∫ Average score ∠ABD (known)

∴∠ABE=∠DBE (definition of angular bisector)

∴∠C=∠D (equivalent substitution)