Posted by tops on .
Outside of circle Γ, point A is chosen. Tangents AB and AC to Γ are drawn, with B,C on the circumference of Γ. On the extension of AB, D is a point such that B is between A and D, and ∠ADC=25∘. The circumcircle of ADC intersects Γ again at E (different from point C ). F is the foot of the perpendicular from B to DC. What is the measure (in degrees) of ∠DEF?