MathNet 2016-part-03 — 184 problems (EN–VI) Question 52

In parallelogram $ABCD$, $AB = 1$, $BC = 4$, and $\angle ABC = 60^\circ$. Suppose that $AC$ is extended from $A$ to a point $E$ beyond $C$ so that triangle $ADE$ has the same area as the parallelogram. Find the length of $DE$.