Vector Dot Product

Click on the window and move the points to change the vectors u and v

The absolute value of the dot product is represented by the shaded area
of the rectangle. If the vectors point in the same direction, the dot product is
positive. If they are perpendicular, the dot product is zero. If the vectors point
in opposite directions, the dot product is negative.

Dr. John Gresham, Created with GeoGebra