ANSWER
[tex]\cos( \angle \: F) = \frac{5}{13}[/tex]
EXPLANATION
The side length adjacent to <F is 5 units.
The length of the hypotenuse is 13 units.
The cosine ratio is
[tex] \cos( \angle \: F) = \frac{adjacent}{hypotenuse} [/tex]
This implies that:
[tex] \cos( \angle \: F) = \frac{5}{13}[/tex]
The fourth choice is correct.
