Answer:
62°
Step-by-step explanation:
If mEF=56°, then ∠EOF=56° as central angle subtended on the arc EF.
Consider isosceles triangle FOE (this triangle is isosceles, because OF=OE as radii of the circle k(O)). In this triangle, angles adjacent to the base EF are congruent. Since the sum of the measures of all interior angles in triangle is 180°, then
m∠EFO=m∠OEF=1/2(180°-56°)=62°.
Actually, point D is extra to solve this question.
