use the pythagorean theorem a.k.a[tex] {a}^{2} + {b}^{2} = {c}^{2}[/tex]
c is the hypotenuse while a & b are the legs
[tex]{15}^{2} + {b}^{2} = {17}^{2} [/tex]
[tex]225 + {b}^{2} = 289[/tex]
subtract 225 from 289
[tex] {b}^{2} = 64[/tex]
square root both b and 64
the other leg is equal to 8
