# Plane geometry problem with parallel lines

I know that i have two parallel lines ($d$ and $d'$) and a secant ($a$), the secant makes extern and intern angle that ar somehow congruent.

I'm thinking, is true that if i have two lines ($d$ and $d'$) (not knowing that are paralel) and a secant ($a$) as, $a \cap d =${$A$} and $a \cap d' =${$B$}, and I know that intern acute angles are congruent, this implies that $d$ and $d'$ are parallel?