If given 3 side lengths, how can you tell if it will make a right triangle?

If the side lengths satisfy the Pythagorean theorem, they will form a right triangle.

That is, the sum of the squares of the short sides must equal the square of the long side.

This is a right angled triangle because one of its angle is 90 degree, Here Angle B is 90 degree.

If any traingle is having 90 degrees then it must be right angled triangle.