### 11.2.3 Draw unit vectors in the plane:
Ox_2d_unit_vector
Oy_2d_unit_vector
frame_2d

The Ox_2d_unit_vector command draws the unit vector in
the x-direction on a plane.

Input:

Ox_2d_unit_vector()

Output:

Similarly, the Oy_2d_unit_vector command
draws the unit vector in the y direction.
The frame_2d command simultaneously draws both unit
vectors.