Area of a rhombus

Area A =
d1 x d2 / 2

Diagonal 1 = d1
Diagonal 2 = d2
AB = BC = CD = DA = c

Example

Take a rhombus with diagonal 1 d1 = 8 cm and diagonal 2 d2 = 3 cm.
Area A of the rhombus =
d1 x d2 / 2
=
8 x 3 / 2
= 12 cm²

Calculate the area of a circle

Diagonal 1
Diagonal 2
Area of the rhombus