parametriche
x = √2 /√(1+k^2)
y= k*√2 /√(1+k^2)

x^2 = 2/(1+k^2)
y^2=2k^2 / (1+k^2)

x^2+y^2 = 2(1+k^2)/(1+k^2) = 2
cartesiana
x^2 +y^2 = 2

a = CurveCartesian(sqrt(2) / sqrt(1 + k^(2)), k * sqrt(2) / sqrt(1 + k^(2)), k, -4, 4)
b = CurveCartesian((-sqrt(2)) / sqrt(1 + k^(2)), k * sqrt(2) / sqrt(1 + k^(2)), k, -4, 4)