### 12.13.3 Check if lines and/or planes in space are parallel: is_parallel

See section 11.16.11 for checking for parallels in two-dimensional geometry.

The is_parallel command takes as arguments two lines, two planes or a line and a plane.

is_parallel returns 1 is the objects are parallel; it returns 0 otherwise.

Input:

L1 := line([0,0,0],[-1,-1,-1])
L2 := line([2,3,-2],[-1,-1,-1])

then:

is_parallel(L1,L2)

Output:

0

Input:

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

then:

is_parallel(P,L2)

Output:

1

Input:

P1 := plane([0,0,0],[1,2,-3],[1,1,-2])
P2 := plane([1,1,0],[2,3,-3],[2,2,-2])

then:

is_parallel(P1,P2)

Output:

1