Representing the information in a diagram, we have:
The given sides are hypotenuse=6 and opposite=4.
The trigonometry ratio Cos is given as:

We will use the pythagoras theorem to obtain the adjacent side.
Thus, we have:
![\begin{gathered} H^2=A^2+O^2 \\ 6^2=A^2+4^2 \\ 36=A^2+16 \\ 36-16=A^2 \\ 20=A^2 \\ A=\sqrt[]{20} \\ A=4.472 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/1f979lkjy48yihtipos81fkngyryq8v4e5.png)
The Cos A is :

Hence, Cos A is 0.745