### 26.14.7 Inversion in the plane

See Section 27.12.7 for inversions in space.

Given a circle C with center P and radius r, the inversion of a point A with respect to C is the point A′ on the ray PA satisfying PA·PA′=r2.

The inversion command creates an inversion.

- inversion takes two mandatory arguments and one optional argument:
  - P, a point (the center of the inversion).
  - r, a real number (the radius).
  - Optionally, G, a geometric object.
- inversion(P,r) returns a new command which performs the inversion.
- inversion(P,r,G) returns and draws the inversion of G.

#### Example

inver:=inversion(i,2); inver(circle(1+i,1))

or:

inversion(i,2,circle(1+i,1))

then:

inver(circle(1+i,1/2))