Rhomboid or deltoid is a convex quadrilateral that is symmetric with respect to at least one of its diagonals (meaning adjacent sides are equal, and diagonals intersect at a right angle).
Special cases of a rhomboid:
Area of a rhomboid through diagonals:
$$S=\frac{d_{1} \times d_{2}}{2},$$
where d1, d2 are the diagonals of the rhomboid.
Area of a rhomboid through two sides and the included angle:
$$S=ab \times \textrm{sin}(\phi),$$
where,
a, b— different sides of the rhomboid.
φ— the angle between the sides.