to find the hypotenuse of a right triangle, we will want to use the Pythagorean Thereom
this thereom is simply the equation..
[tex] {a}^{2} + {b}^{2} = {c}^{2} [/tex]
so by using the info in the question, we get..
[tex] {5}^{2} + {8}^{2} = {c}^{2} [/tex]
now we square the numbers..
[tex]25 + 64 = {c}^{2} [/tex]
and add..
[tex]89 = {c}^{2} [/tex]
now simply take the square root of each side..
[tex]c = \sqrt{89} [/tex]
[tex]hypotenuse = \sqrt{89} [/tex]