Answer:
Step-by-step explanation:
In the given triangle, side DE is the hypothenuse. So, we can use Pythagorean's Theorem, where both legs are 3 units long.
[tex]DE^{2}=DF^{2}+EF^{2}\\ DE^{2}=3^{2}+3^{2}\\DE^{2}=9+9\\DE=\sqrt{18} \approx 4.2[/tex]
Therefore, the side DE is 4.2 units long, approximately.
