# The difference and sum of two points in the plane:+ -

### 13.6.3 The difference and sum of two points in the plane:+ -

Let A and B be two points in the plane, with affixes a1 + i a2 and b1 + ib2 respectively.
Input:

A:= point(1 + 2*i); B:= point(3+4*i)

Then:

- The difference B−A returns the affix (b1−a1)+i(b2−a2), which represents the vector AB.
  Input:
  vector(A,B); vector(point(0),point(B-A))
  Output:
- The sum B+A returns the affix (b1+a1)+i(b2+a2). If D:= point(B+A), then BD = OA.
  Input:

  D:= point(B + A);
  segment(B,D); segment(point(0),A)

  Output:

Note that −A is the point symmetrical to A with respect to the origin.

The sum of three points A + B + C can be viewed as the translate of C by the vector A + B. So if A or B contains parameters, you should write this as C + (A + B) or evalc(A + B) + C.