- Calculus, Volume 1: One Variable Calculus, with an Introduction to Linear Algebra
- Tom M. Apostol
- Second Edition
- 1967
- 978-1-119-49673-1
13.25. Miscellaneous review exercises on conic sections
- Show that the locus of the centers of a family of circles, all of which are tangent (externally) to a given circle and also to a given straight line, is a parabola. (Exercise 21 can be considered to be a special case.)
- This solution follows the same logic as that of (13.25.21)
- We know that a parabola is symmetric about its axis, thus the chord of length $8|c|$ can be broken down into two chords of length $4|c|$