A function of two two-dimensional vectors, returning a scalar. The slash product is the two-dimensional analogue of the three-dimensional cross product.

Given two vectors a = [dxa, dya] and b = [dxb, dyb]

a / b = dxbdya - dxadyb

The value of the slash product is always the magnitude of the vector returned by the cross product of equivalent three-dimensional vectors:

a / b = |a| |b| sin θ

where |b| id the magnitude of vector a, |b| is the magnitude of vector b, and θ is the angle which, applied to the direction of vector a, would produce the direction of vector b.

This is also the area of a parallelogram whose sides have the direction and magnitude of the two vectors, two sides for each vector.

It's very useful since |b| sin θ is used for calculating the perpendicular distance from a point to a line segment.