When we draw a circle with the centre at D and have a tangent HF to the circle D at point E, the angle DEF will be a right angle.
In other words angle DEF = 90 degrees
Since HF, the tangent, is a straight line, the other angle DEH should also be = 90 degrees because the straight line has an angle of 180 degrees
Therefore angle DEF = angle DEH = 90 degrees
Therefore, angle DEF is congruent to angle DEH (Option A)
