TeX source:
\begin{array}{rcl} b &=& \sqrt{\left(\dfrac{f}{2}\right)^2+(e-p)^2} \cr b &=& \sqrt{\left(\sqrt{3} \, cm\right)^2+(7 \, cm-1 \, cm)^2} \cr b &=& \sqrt{39} \, cm \end{array}