Because A and E are corresponding angles, the sides opposite them are corresponding. So $\displaystyle{\overline{{{B}{C}}}}\leftrightarrow{\overline{{{F}{D}}}}\usepackage{cmbright}\Huge\$ . Because B and F are corresponding angles, the sides opposite them are corresponding. So $\displaystyle{\overline{{{A}{C}}}}\leftrightarrow{\overline{{{E}{D}}}}.\usepackage{cmbright}\Huge\$ Because two pairs of corresponding angles have the same measures ( $\displaystyle{m}\angle{A}={m}\angle{E}\usepackage{cmbright}\Huge\$ and $\displaystyle{m}\angle{B}={m}\angle{F}\usepackage{cmbright}\Huge\$ ), the third pair of corresponding angles must be congruent. So $\displaystyle\angle{C}\leftrightarrow\angle{D}\usepackage{cmbright}\Huge\$ , and therefore $\displaystyle{\overline{{{A}{B}}}}\leftrightarrow{\overline{{{E}{F}}}}\usepackage{cmbright}\Huge\$ .