### 11.11.2 Circular arcs: arc

See also section 11.11.1

The arc command takes three mandatory arguments and one or two optional
arguments. The mandatory arguments are two points A
and B and a real number a between −2π and 2π.

arc returns and draws the circular arc from A to
B that represents and angle of a.
(Note that the center of the circle will be
(A + B)/2 + i*(B - A)/(2*tan(a/2)).)

Input:

arc(1,i,pi/2)

Output:

Input:

arc(1,i,-pi/2)

Output:

The optional arguments need to be
variable names which will be assigned to the center and
the radius of the circle.