name extended coordinates
variable X
variable Y
variable Z
variable XX
variable YY
variable ZZ
variable XY
variable YZ
variable XZ
satisfying x = X/Z
satisfying y = Y/Z
satisfying XX = X X
satisfying YY = Y Y
satisfying ZZ = Z Z
satisfying XY = 2 X Y
satisfying XZ = 2 X Z
satisfying YZ = 2 Y Z