pencil, paper, ruler
Draw:-[tex]\begin{align*}\triangle ABC\end{align*}.[/tex] Label the vertices.
[tex]\begin{align*}\overline{XY}\end{align*} so that \begin{align*}X\end{align*} is on \begin{align*}\overline{AB}\end{align*} and \begin{align*}Y\end{align*} is on \begin{align*}\overline{BC}\end{align*}. \begin{align*}X\end{align*} and \begin{align*}Y\end{align*}[/tex] can be anywhere on these sides.
Draw:-
a second triangle,[tex] \begin{align*}\triangle DEF\end{align*}.[/tex] Label the vertices
Draw:-
[tex]\begin{align*}\overline{XY}\end{align*} so that \begin{align*}X\end{align*} is on \begin{align*}\overline{DE}\end{align*} and \begin{align*}Y\end{align*} is on \begin{align*}\overline{EF}\end{align*} AND \begin{align*}\overline{XY} \ || \ \overline{DF}\end{align*}.
Is \begin{align*}\triangle XEY \sim \triangle DEF\end{align*}? Why or why not? Measure \begin{align*}DX, XE, EY,\end{align*} and \begin{align*}YF\end{align*}. Then set up the ratios \begin{align*}\frac{DX}{XE}\end{align*} and \begin{align*}\frac{FY}{YE}\end{align*}.[/tex] Are they equal?
