Question 314626
The diagonal is the hypotenuse of a right triangle.


{{{5^2 + 4^2=d^2}}}
{{{25 + 16= d^2}}}
{{{d^2=41}}}
{{{d=sqrt(41)}}} or  {{{d=-sqrt(41)}}}


Reject the second solution because the hypotenuse cannot be negative.


Final answer ={{{sqrt(41)}}}.


Dr. Robert J. Rapalje