HP Prime Graphing Calculator - Manual (Page 193)

Geometry 189
is_square
Tests whether or not a set of four points are vertices of a
square. Returns 1 if they are and 0 otherwise.
is_square(point1, point2, point3, point4)
Example:
is_square(point(0,0), point(4,2),
point(2,6), point(-2,4)) returns 1.
Other Geometry functions
The following functions are not available from a menu in the
Geometry app, but are available from the Catlg menu.
convexhull
Returns a vector containing the points that serve as the convex
hull for a given set of points.
convexhull(point1, point2, …, pointn)
harmonic_conjugate
Returns the harmonic conjugate of 3 points. Specifically,
returns the harmonic conjugate of point3 with respect to
point1 and point2. Also accepts three parallel or concurrent
lines; in this case, it returns the equation of the harmonic
conjugate line.
harmonic_conjugate(point1, point2, point3)
or
harmonic_conjugate(line1, line2, line3)
Example:
harmonic_conjugate(point(0, 0), point(3, 0),
point(4, 0)) returns point(12/5, 0)
harmonic_division
Returns the harmonic conjugate of 3 points. Specifically,
returns the harmonic conjugate of point3 with respect to
point1 and point2 and stores the result in the variable var.
Also accepts three parallel or concurrent lines; in this case, it
returns the equation of the harmonic conjugate line.
harmonic_division(point1, point2, point3, var)
or
harmonic_division(line1, line2, line3, var)