# SOLUTION: Find the area of trapezoid ABCD if the vertices are A(1,5), B(7,3),C(2,-4), and D(-7,-1)

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 Question 631915: Find the area of trapezoid ABCD if the vertices are A(1,5), B(7,3),C(2,-4), and D(-7,-1)Answer by Alan3354(30993)   (Show Source): You can put this solution on YOUR website!Find the area of trapezoid ABCD if the vertices are A(1,5), B(7,3),C(2,-4), and D(-7,-1) ----------- Do these like this: +A +B +C +D +A +1 +7 +2 -7 +1 +5 +3 -4 -1 +5 ------- Add the diagonals starting at the upper left. = 1*3 + 7*-4 + 2*-1 + -7*5 = 3 - 28 - 2 - 35 = -62 --------- Add the diagonals starting at the lower left. = 5*7 + 3*2 + -4*-7 + -1*1 = 35 + 6 + 28 - 1 = +68 -------- Then, Area = 1/2 the absolute value of the difference Diff = 130 Area = 65 sq units. =========================== This works for all polygons, any number of sides.