From the given right-angle triangle, with a = 9.79, b = 11.37, c = 15, we have:
[tex]\begin{gathered} \sin \phi=\frac{a}{c} \\ \\ =\frac{9.79}{15}=0.65 \end{gathered}[/tex][tex]\begin{gathered} \cos \phi=\frac{b}{c} \\ \\ =\frac{11.37}{15}=0.76 \end{gathered}[/tex][tex]\begin{gathered} \tan \phi=\frac{a}{b} \\ \\ =\frac{9.79}{11.37}=0.86 \end{gathered}[/tex]Finally, we can obtain the value:
[tex]\begin{gathered} \phi\text{ as} \\ \phi=\sin ^{-1}0.65 \\ =0.71\text{ radians} \end{gathered}[/tex]