What is this formula involving circles trying to do?

Question

x, y, z = pos
radius = width / 2.0
if width >= 0.0:
    x = -x
a = radius * math.pi
a = (x/a) * math.pi

This is a code snippet from someone other than me, and I've been wanting to understand it. However, the variable a is a little ambiguous, and I'm having trouble figuring out its purpose.

This snippet is part of a function that calculates an arch that text will be displayed over.

The variable pos is the position of the current letter we are working with. The variable width is the width of the entire line.

Answer 1

There is nonsense usage of math.pi - result doesn't depend on it.
a = x/R = Cos(Fi), where Fi is direction angle of (coordinate origin - starting point) vector, if R is radius of arc with origin as center

(Cos(Fi) negated for positive width values)