Question 1146602
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If one of the diagonals is equal to the side length, then that diagonal divides the rhombus into two equilateral triangles.<br>
The other diagonal of the rhombus is composed of the heights of the two equilateral triangles.  Each of those heights has a length equal to sqrt(3)/2 times the side length; so the length of the other diagonal is sqrt(3) times the side length.<br>
Then the area of a rhombus is half the product of the lengths of the diagonals.<br>
You can put those pieces together, along with the given length of the longer diagonal, to finish the problem.