Using the geometric mean theorem,we have:
[tex]\begin{gathered} \frac{DC}{4}=\frac{4}{2} \\ \frac{DC}{4}=2\text{ (Dividing)} \\ DC=2\cdot4(\text{Multiplying by 4 on both sides of the equation)} \\ DC=8(\text{Multiplying)} \\ \text{The answer is DC=8} \end{gathered}[/tex]