Check the picture below.
[tex]\textit{using the pythagorean theorem} \\\\ d^2=a^2+b^2\implies c = \sqrt{a^2+b^2} \qquad \begin{cases} d=hypotenuse\\ a=adjacent\\ b=opposite\\ \end{cases} \\\\\\ d = \sqrt{3^2+4^2}\implies d = \sqrt{9+16}\implies d = \sqrt{25}\implies d = 5\implies \stackrel{\textit{rounded up}}{d = 5.0}[/tex]
