1) Quadrilateral PAST, TX=AX, [tex]\overline{TP} \parallel\overline{AS}[/tex] (given)
2) [tex]\angle XPT \cong \angle XSA[/tex] and [tex]\angle XTP \cong \angle XAS[/tex] (alternate interior angles theorem)
3) [tex]\triangle TXP \cong \triangle AXS[/tex] (AAS)
4) [tex]\overline{TP} \cong \overline{AS}[/tex] (CPCTC)
5) PAST is a parallelogram (a quadrilateral with two pairs of opposite congruent sides is a parallelogram)
