To find any missing length in a right triangle, we use the Pythagorean Theorem:

Where a is the length of the hypotenuse, the longest side.
In the given right triangle:
• a=8.9
,
• b=4
,
• c=8
We check if this satisfies the Pythagorean Theorem:
![\begin{gathered} a^2=4^2+8^2 \\ a^2=16+64 \\ a^2=80 \\ a=\sqrt[]{80} \\ a=8.9\text{ units} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/cjufozbkwsm08llvxw4fas92m6p5lwseni.png)
Thus, we see that the Pythagorean Theorem holds.