xx = 1 (slider from 0 to 3, step 0.1)
A = (-1, 0)
M: (xx, 0)
B_1 = Midpoint(A, M)
c = Circle(B_1, M)
C_1, B = Intersect(c, yAxis)
b = OrthogonalLine(B, yAxis)
d = OrthogonalLine(M, xAxis)
C = Intersect(b, d)
lieu2 = Locus(C, xx)