Parameters:
[tex]\begin{gathered} \tan \theta=\frac{5}{12} \\ \end{gathered}[/tex]From the above diagram, we can obtain the length of the hypotenuse by using the Pythagorean theorem
[tex]\begin{gathered} x=\sqrt[]{12^2+5^2} \\ \\ =13 \end{gathered}[/tex]Now,
[tex]\begin{gathered} \cos \theta=\frac{\text{adjacent}}{\text{hypotenuse}} \\ \\ =\frac{12}{13} \end{gathered}[/tex]