A right trapezoid has parallel sides AB and CD (AB > CD), a perpendicular side AD. The diagnoal AC equals to the side AB and the side AD equals to the side DC. A line through C, perpendicular to side BC intersects side AD in the point F. Find the area of the trapezoid if we know that DF=1.

Can someone please tell me how to set this problem up? I can solve it from there...

Thank you.