Hypotenuse be H
Apply Pythagorean theorem
[tex]\\ \tt\hookrightarrow H^2=P^2+B^2[/tex]
[tex]\\ \tt\hookrightarrow H^2=4^2+4^2[/tex]
[tex]\\ \tt\hookrightarrow H^2=32[/tex]
[tex]\\ \tt\hookrightarrow H=\sqrt{32}[/tex]
[tex]\\ \tt\hookrightarrow H=5.8units[/tex]