Solution :
Since, PM \(\perp\) QR, therefore,
\(\triangle\) PQM ~ \(\triangle\) RPM
\(\implies\) \(PM\over QM\) = \(MR\over PM\)
So, \({PM}^2\) = QM.MR.
Since, PM \(\perp\) QR, therefore,
\(\triangle\) PQM ~ \(\triangle\) RPM
\(\implies\) \(PM\over QM\) = \(MR\over PM\)
So, \({PM}^2\) = QM.MR.