Rhombus and trapezoid area
1. Area of rhombus
In the rhombus of the picture, the greater diagonal is AC and the less diagonal is BD. If we draw in the four vertices the parallels to the diagonals, we obtain a rectangle whose side is the less diagonal BD and whose height is the greater diagonal AC. If we call the diagonals d and D, the area of the rectangle will be d x D, which has 8 triangles. As the rhombus has the four interior triangles, its area will be the half of the rectangle: D x d/2.
The area of a rhombus is equal to half a product of lengths of two diagonals.
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