Answer:

Explanation:
Let's illustrate the situation in a diagram to understand.
In a right triangle if the altitude drawn divides the hypotenuse into two segments, then the length of the altitude is the geometric mean of the lengths of the two segments.
Therefore,
![\begin{gathered} (8)/(a)=(a)/(2) \\ 2\cdot8=a^2 \\ 16=a^2 \\ a=\sqrt[]{16} \\ a=4\text{ cm} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/lqbhpjsyyzzz34qyhnhmqa776c891h0b8i.png)