Lemar is completing a proof of the law of sines. His first step is shown.

The first step shows that h = zsin(X). Next, we can do the same with angle Z to get:
[tex]sin(Z)=\frac{h}{x}\Rightarrow h=xsin(Z)[/tex]now that we have that h = zsin(X) and h = xsin(Z), we can equate both expressions to get:
[tex]\begin{gathered} zsin(X)=xsin(Z) \\ \Rightarrow\frac{z}{sin(Z)}=\frac{x}{sin(X)} \end{gathered}[/tex]