# Astroid Calculator

An astroid is a flat curve described by a point of a circle of radius rolling along the inner side of a circle of radius. In other words, an astroid is a hypocycloid with a module. The name of the curve in the form of “Astrois”.

**Octagon Calculator**

**The radius of the larger circle (a)**

**The radius of the smaller circle (b)**

**Chord length (l)**

**Perimeter (p)**

**Square (S)**

## Formulas

b = a / 4

l = 2 * a * sin( π/4 )

Р = 6 а

S = 3/8 π a2