The tangents drawn from the origin to the circlex2+y2−2rx−2hy+h2=0 are perpendicular, if

The combined equation of the tangents drawn  from (0,0) to x2+y2−2rx−2hy+h2=0, isx2+y2−2rx−2hy+h2h2=−rx−hy+h22This equation represents a pair of perpendicular straight lines if Coeff. of x2+ Coeff. of y2=0⇒ 2h2−r2−h2=0⇒r2=h2⇒r=±h