The Heron’s formula to find area of a quadrilateral is [√s1(s1 - a)(s1 - b)(s1 - e)] + [√s2(s2 - d)(s2 - c)(s2 - e)] where s1 is the semi-perimeter of one triangle and s2 is the semi-perimeter of another triangle. a,b,c,d are the sides of the quadrilateral and e is the length of the diagonal.

Heron’s formula is used to find the area when the lengths of the four sides are given along with the diagonal length.