You have
x^2 + (y+f)^2 = f^2-1
These are circles with center at (0,-f). Clearly the radii of these circles are orthogonal to the curves, and that is the family of lines that pass through (0,-f):
y+f = mx
find orthogonal trajectory of family of circles x^2+y^2+2fy+1=0.
7 answers
X^2+y^2-cx-100
x2+2y2=c2
x2+y2-c1y=c
Answer for this problem
Orthogonal trajectory of x^2+y^2+2fy+1=0 please give me answer
Give me answer