The given expression is
[tex]3\cos \theta=0.714[/tex]First, we divide the equation by 3
[tex]\begin{gathered} \frac{3\cos \theta}{3}=\frac{0.714}{3} \\ \cos \theta=0.238 \end{gathered}[/tex]Then, we find theta
[tex]\begin{gathered} \theta=\cos ^{-1}(0.238) \\ \theta=1.33\text{rad} \end{gathered}[/tex]