I have a geometry question which I have a lot of difficulty doing the question is in Italian and I can kind of understand it but it is still troubling me. could someone explain it to me please ? Here is what Google translate says :
Given an ABC triangle, the bisectors of the outer angles B and C lie on the opposite side of A with respect to BC. Let D be their intersection and E, F the intersections of the parallel to BC through D, with the extensions of the AB and AC sides. Show that EF = EB + FC.
Here is the original text :
Dato un triangolo ABC, si conducano le bisettrici degli angoli esterni B e C che giacciono sulla parte opposta di A rispetto a BC. Detta D l loro intersezione ed E, F i punti di incontro della parallela per D a BC con i prolungamenti dei lati AB e AC, dimostrare che EF = EB + FC.
Thank you in advance.

The triangles $BED$ and $CFD$ are isosceles.