The cosine ratio is given by the following formula:
[tex]\cos (Z)=\frac{\text{adjacent leg}}{hypotenuse}[/tex]
The adjacent leg of angle Z is side ZY=12 and the hypotenuse of the triangle is the side XZ=20, thus the cosine ratio of Z is:
[tex]\cos (Z)=\frac{12}{20}[/tex]
