We have to find AB.
As we have a right triangle, we can use trigonometric ratios to relate trigonometric functions with the length of the sides.
In this case, we use the angle [tex]\begin{gathered} \cos (\alpha)=\frac{\text{Adyacent}}{\text{Hypotenuse}} \\ \cos (A)=\cos (42\degree)=\frac{AC}{AB}=\frac{10}{AB} \\ \cos (42\degree)=\frac{10}{AB} \end{gathered}[/tex]Answer:
cos(42º)=10/AB [Option D]
