The answer to, Is the Triangle with side lengths of 10 in., 24 in., and 26 in, a right triangle is: Yes. For right triangles, the sum of the squares of the shorter sides is equal to the square of the longer side. Thus, this is a right triangle if 10^2+24^2=26^2. Expanding these squares, we have 100+576=676, which is true. Thus, the triangle is right.