How to tell if a triangle is right obtuse or acute with side lengths?

Using Pythagorean theorem we can easily get to know about the triangle.

If  c^2=a^2 + b^2   Then triangle is Right Angled.
If  c^2 > a^2 + b^2  Then triangle is obtuse triangle
and when c^2 < a^2 + b^2 , it means triangle is acute triangle.
( Here a= adjacent, b= opposite and c=hypotenuse of triangle)