Since we have a right-angled triangle, we can use the Pythagoras Theorem:
[tex]a^2+b^2=c^2[/tex]
where a and b are the shorter sides of the triangle and c is the hypotenuse.
a = x; b = 3 mi; c = sqrt(10).
We substitute our values and then we solve for x:
[tex]\begin{gathered} x^2+3^2=(\sqrt[]{10})^2 \\ x^2=10-3^2 \\ x^2=1 \\ x=1 \end{gathered}[/tex]
Therefore, the missing side of the triangle is 1 mi.
