Answer: Last option.
Step-by-step explanation:
You must apply [tex]cos\alpha=\frac{adjacent}{hypotenuse}[/tex]
Then, given the right triangle shown in the image attached and the angle K, the adjacent side and the hypotenuse of the triangle are the following:
[tex]adjacent=5\\hypotenuse=13[/tex]
Therefore, when you substitute values into [tex]cos\alpha=\frac{adjacent}{hypotenuse}[/tex] you obtain that cosK is the shown below:
[tex]cosK=\frac{5}{13}[/tex]
Therefore, the answer is the last option.
