# Math Help - part two of the hard question trigiolgy

1. ## part two of the hard question trigiolgy

A is a fixed pt on a given circle; AP , AQ are variable chords such that AP.AQ is constant. Prove that PQ touches a fixed circle, centre A

2. Originally Posted by calculus_jy
A is a fixed pt on a given circle; AP , AQ are variable chords such that AP.AQ is constant. Prove that PQ touches a fixed circle, centre A
Hello,

unfortunately I can't give you a proof of this statement.

I've sketched a few different situations and obviously the statement seems to be true. With the drawing (see attachment) I choose:

R = 6 cm
$|AP| \cdot |AQ| = 48$. Then I got the radius of the circle with centre A is 4 cm long. Probably there exists the "rule"(?):

$r = \frac{|AP| \cdot |AQ|}{2R}$