Answer:
[tex]4 \sqrt{2} [/tex]
Step-by-step explanation:
A square has 4 equal sides.
When you draw a diagonal line in the square, it creates two triangles.
The two sides of the triangle would be 4 and the hypotenuse would be the diagonal.
To find the hypotenuse you use
[tex]a {}^{2} + b {}^{2} = c {}^{2} [/tex]
So
[tex]4 {}^{2} + 4 {}^{2} = c {}^{2} [/tex]
Solve
[tex]16 + 16 = c {}^{2} \\ 32 = c {}^{2} \\ \sqrt{32} = c \\ c = 4 \sqrt{2} [/tex]