posted by anthony .
The cross section of an attic is in the shape of an isosceles trapezoid. If the height of the attic is 9 feet, BC=12 feet, and AD=28 feet, find the length of line AB to the nearest foot.
The triangle of the trapezoid is triangle ABE and the bases are BC and AD.
Could you also give me a link about the theorems and postulates of a two column proof?