Draw two lines vertically down from side "A" to "B"...you now have three objects ... to triangles, and one rectangle.... the area of the rectangle is "AH"...now you have two triangles, that have area 1/2 base*height... the height is "H" and the base .... well it is (B-A)/2... so the area of the two triangles are ..... (2)*(1/2)*((B-A)/2)* H.... The total area is .... AH + (2)*(1/2)*((B-A)/2)* H .... 2* 1/2 = 1 so now we have AH + ((B-A)/2)* H .... to help see this let us write it as AH + H(B-A)/2 .. expand the right H.... AH + BH/2 - AH/2.......
According to the trapezoid area formula, the area of a trapezoid is equal to half the product of the height and the sum of the two bases. Area = ½ x (Sum of parallel sides) x (perpendicular distance between the parallel sides).
