1) Notice that angles 1 and 2 are alternate interior angles.
2) Since l⊥p, and m⊥p then
[tex]\begin{gathered} \measuredangle1=90^{\circ}. \\ \measuredangle2=90^{\circ}. \end{gathered}[/tex]3) Since ∡1=90 degrees and ∡2=90 degrees, using the transitive property we get that:
[tex]\measuredangle1=\measuredangle2.[/tex]4) Since the alternate interior angles are equal, then l║m.