A rhombus is a special type of quadrilateral. All the sides of a rhombus are the same length, and the diagonals are perpendicular and the same length. The diagonals bisect the angles and their point of intersection is the centre of the rhombus. The formula for the area of a rhombus is：

The formula for the area of a rhombus is S = (d1 × d2) / 2, where d1 and d2 are the lengths of the two diagonals of the rhombus. The area of a rhombus is equal to half the product of the lengths of its two diagonals.

The area of a rhombus is equal to half the product of its two diagonals.

If a and b represent the two diagonals of the rhombus, then the area of the rhombus is:

The method of calculating the area of a rhombus is as follows: divide the rhombus into two isosceles triangles, use the Pythagorean theorem to find the area of each triangle, add the areas of the two triangles to obtain the area of the rhombus, and then substitute the property of the rhombus that the lengths of its diagonals are equal to obtain the formula for the area, which is the product of the lengths of the diagonals divided by two.

For example, if a rhombus has diagonal lengths of 5 centimeters and 7 centimeters, respectively, then its area is (5×7) ÷ 2 = 17.5 square centimeters