Answer:
[tex]cosZ=\frac{3}{5}[/tex]
Step-by-step explanation:
Cos of an angle by definition of its ratio is side adjacent/hypotenuse. The side adjacent to angle Z cannot be the hypotenuse, so it has to be 6. The hypotenuse is 10. Therefore,
[tex]cosZ=\frac{6}{10}=\frac{3}{5}[/tex]