An equilateral parallelogram whose acute angles are 
.
Sometimes, the restriction to 
is dropped, and it is required only that two opposite angles are acute and the other
two obtuse. The term rhombus is commonly used for an
arbitrary equilateral parallelogram.
The area of a lozenge of side length 
is
 |
(1)
|
its diagonals have lengths
 |  |  |
(2)
|
 |  |  |
(3)
|
and it has inradius
 |
(4)
|
