So we are looking for side [tex]z[/tex] and we are given the length of hypotenuse ([tex]b=18[/tex]) and angle [tex]\zeta=60[/tex].
The function I would use is sine.
[tex]\sin(\zeta)=\frac{z}{b}[/tex]
If we solve for side [tex]z[/tex]:
[tex]z=b\times\sin(\zeta)[/tex]
Now fill in the data.
[tex]z=18\times\sin(60)\approx\boxed{15.59}[/tex]
