A right triangle can't be an obtuse triangle.
An obtuse triangle is a triangle with an obtuse angle (greater than 90 degrees)
in it. A right triangle always has one right angle in it (90 degrees), so it can't
also have another angle that's greater than 90 degrees ... that would make the
sum of the angles in the triangle greater than 180 degrees, which we know to be
a big no-no.
