Philip P. answered 11/21/21
Affordable, Experienced, and Patient Geometry Tutor
You applied the Triangle Inequality Theorem, which proves you can make a triangle with sides 5, 7, and 10; but it does not prove it's a right triangle. To do that, you apply the Pythagorean Theorem. If 52 + 72 = 102, it's a right triangle. Otherwise it isn't.