Respuesta :
Step-by-step explanation:
in a square 2 sides with a diagonal creates a right-angled triangle, with the diagonal being the Hypotenuse (the side opposite of the 90° angle).
the diagonal is 3+3 = 6 units long.
let's call the square side length "s".
then we have via Pythagoras
6² = s² + s² = 2s²
36 = 2s²
18 = s²
s = 4.242640687 ≈ 4.2 units