# Checking if an object in space is on another object: is_element

### 14.13.1 Checking if an object in space is on another object: is_element

See Section 13.16.1 for checking elements in two-dimensional geometry.

The is_element command determines whether or not a geometric object is contained in another.

- is_element takes two arguments:
  G,H, two geometric objects.

- is_element(G,H) returns 1 if G is contained in H and returns 0 otherwise.

#### Examples.

- Input:

  P:= plane([0,0,0],[1,2,-3],[1,1,-2])
  is_element(point(2,3,-5),P)

  Output:

  1

- Input:

  L:= line([2,3,-2],[-1,-1,-1]);
  P:= plane([-1,-1,-1],[1,2,-3],[1,1,-2]);
  is_element(L,P)

  Output:

  0