Answer
See the picture below:
Work Step by Step
If we imagine, that $\angle DEF=90^{\circ}$ we only have to construct the angle bisector.
By using a compass mark an arc to intersect the sides of $\angle DEF$. Now with those two points as centers, mark off two arcs with equal radii to intersect point $A$. Connect this point with E to get the angle bisector.
