The quadrifolium (also known as four-leaved clover[1]) is a type of rose curve with an angular frequency of 2. It has the polar equation:

Rotated quadrifolium
Quadrifolium created with gears
This article is about the geometric shape. For the plant, see
Four-leaf clover. For the symmetrical shape framework, see
Quatrefoil.
with corresponding algebraic equation

Rotated counter-clockwise by 45°, this becomes

with corresponding algebraic equation

In either form, it is a plane algebraic curve of genus zero.
The dual curve to the quadrifolium is

Dual quadrifolium
The area inside the quadrifolium is
, which is exactly half of the area of the circumcircle of the quadrifolium. The perimeter of the quadrifolium is

where
is the complete elliptic integral of the second kind with modulus
,
is the arithmetic–geometric mean and
denotes the derivative with respect to the second variable.[2]