Let ABCD be an isosceles trapezoid with bases AB and CD. The incircle of the triangle BCD touches CD at E. Point F is chosen on the bisector of the angle DAC such that the lines EF and CD are perpendicular. The circumcircle of the triangle ACF intersects the line CD again at G. Prove that the triangle AFG is isosceles. isoscelestrapezoidincircleperpendiculargeometry