As shown in the figure, if the vertices e, F and D of the diamond BEDF are on the edge of △ ABC, and ab = 18, AC = BC = 12, then the perimeter of the diamond is______ .
The four sides of the diamond are equal. Let the length of the side be X. according to DF ∥ BC, we can get dfbc = AFAC, that is, X12 = AFAC. Similarly, x18 = cfac. By adding the two formulas, we can get: X12 + x18 = 1, and the solution is: x = 7.2, so the perimeter is 28.8
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