The point m is on AB, the quadrilateral AMCD and the quadrilateral BMDC are parallelograms, and MD = MC. Prove that the quadrilateral ABCD is isosceles trapezoid

The point m is on AB, the quadrilateral AMCD and the quadrilateral BMDC are parallelograms, and MD = MC. Prove that the quadrilateral ABCD is isosceles trapezoid

∵ quadrilateral AMCD is parallelogram ∥ ab ∥ CD ∥ must be trapezoid
Another ∵ quadrilateral AMCD is parallelogram ∵ MC = ad ∵ quadrilateral BMDC is parallelogram ∵ MD = BC ∵ MD = MC, so ad = BC is isosceles trapezoid