The figure is a square .This means all the sides are equal in length. And each angle is 90 degrees. BD can be found using pythagora's theorem.
[tex]\begin{gathered} c^2=a^2+b^2 \\ c^2=16^2+16^2 \\ c^2=256+256 \\ c^2=512 \\ c=\sqrt[]{512} \\ c=\sqrt[]{256\times2} \\ c=16\sqrt[]{2} \end{gathered}[/tex]
