triangle is how many degrees
This rectangle has four 90 degree angles adding up to 360 degrees. Since the triangles are congruent each triangle has half as many degrees, namely 180. So this is true for any right triangle. Suppose you triangle is not a right triangle. Draw a perpendicular from the vertex opposite the longest side, to the longest side.
Another interesting right triangle is the 30-60-90 degree triangle. The ratio of this triangle's longest side to its shortest side is two to one.. That is, the longest side is twice as long as the shortest side.