draw any trapezoid
draw a diagonal
isn't the height between the two parallel sides constant? Let it be h
let the two parallel sides be a and b
so now you have two triangles where you know the height, h, and the sides
first triangle area = (1/2)ah
2nd triangle area = (1/2)bh
total = (1/2)ah + (1/2)hb
common factor of (1/2)h
gives us
(1/2)h(a+b)
why the formula for the area of a trapezoid this A=1/2 x h x(a+b)
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