### 12.11.2 Circular arcs: arc

See also section 12.11.1

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.