Hi, I have been having some trouble with this problem, I am not quite sure if this is the right sub-forum, if not please direct me to where I should post it. I put it here as this the geometry forum for university mathematics, although I see it is for Differential Geometry which this is not.

Let F be the midpoint of side BC of a triangle ABC. Construct isosceles right angled triangles ABD and ACE externally on sides AB and AC with the right angles at D and E. Show that triangle DEF is an isosceles right angled triangle.