name Jacobian coordinates with a4=0
assume a = 0
variable X
variable Y
variable Z
neutral X = 1
neutral Y = 1
neutral Z = 0
satisfying ZZ = Z^2
satisfying ZZZ = ZZ*Z
satisfying x = X/ZZ
satisfying y = Y/ZZZ
toaffine x = X/ZZ
toaffine y = Y/ZZZ
tosystem X = x
tosystem Y = y
tosystem Z = 1
homogweight X = 2
homogweight Y = 3
homogweight Z = 1
