(Please help/ hurry) Find the length of the third side, If necessary, write in simplest radical form

Answer:
The length of the third side is 2.
Explanation:
According to figure, we have a right triangle. The missing length can be determined by Pythagorean Theorem:
[tex]r^{2} = s^{2} + l^{2}[/tex] (1)
Where:
[tex]r[/tex] - Hypotenuse.
[tex]s[/tex], [tex]l[/tex] - Legs.
If we know that [tex]r = 2\sqrt{5}[/tex] and [tex]l = 4[/tex], then the missing length is:
[tex]s = \sqrt{r^{2}-l^{2}}[/tex] (2)
[tex]s = \sqrt{20-16}[/tex]
[tex]s = \sqrt{4}[/tex]
[tex]s = 2[/tex]
The length of the third side is 2.