[tex]\theta\propto\frac{1}{r^{}}[/tex][tex]\begin{gathered} \text{adding a constant yields} \\ \theta=\frac{k}{r} \end{gathered}[/tex][tex]\begin{gathered} \text{but }\theta=\text{ 68 and r =4.2} \\ 68=k/4.2^{} \\ k\text{ =}285.6 \end{gathered}[/tex][tex]\begin{gathered} so\text{ } \\ \theta=\frac{285.6}{r} \end{gathered}[/tex]
Now looking for the banking angle when the turning radius is 5.6ft we substitute for r in the above equation
[tex]\begin{gathered} \theta=\frac{285.6}{5.6^{}} \\ \theta=51^{\circ} \end{gathered}[/tex]