1. Suppose that BC is hypotenuse, then by Pythagorean theorem:
[tex]BC^2=AC^2+AB^2, \\ BC^2=3^2+7^2, \\ BC^2=9+49, \\ BC^2=58, \\ BC= \sqrt{58} [/tex].
2. If BC is not hypotenuse, then BC is a leg and AC is hypotenuse (because AC>AB). Hence by Pythagorean theorem:
[tex]AC^2=AB^2+BC^2, \\ 7^2=3^2+BC^2, \\ BC^2=49-9, \\ BC^2=40, \\ BC= \sqrt{40} =2 \sqrt{x10} [/tex].
