geometry
posted by jay .
what is the area of a rhombus if AB equals 9.9 and AC equals 13 and DB equals 15?

Since a rhombus has equal sides, the lines AC and BD intersect at right angles, dividing it into four congruent triangles.
The total area is (4)*(1/2)*(4.45)(6.5)
= (1/2)(9)(13) = 58.5 
I misread the problem by using 9 for one of the diagonals. The answer should be
A = (1/2)(13)(15) = 97.5
Note that you not have to use the value of AB. Its value, for a true rhombus, should be sqrt[(6.5)^2 + (7.5)^2] = 9.92 , which is close to what was given.
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