The slant height of the cone \((l)=\sqrt{h^2+r^2}\)
According to the given condition, \(\cfrac{1}{3} πr^2 h=πrl\)
Or, \(\cfrac{1}{3} rh=l\)
Or, \(l=\cfrac{1}{3} rh\)
Or, \(\sqrt{h^2+r^2}=\cfrac{1}{3} rh\)
Or, \(h^2+r^2=\cfrac{1}{9} r^2 h^2\)
Or, \(\cfrac{h^2+r^2}{r^2 h^2}=\cfrac{1}{9}\)
Or, \(\cfrac{h^2}{r^2 h^2}+\cfrac{r^2}{r^2 h^2}=\cfrac{1}{9}\)
Or, \(\cfrac{1}{r^2} +\cfrac{1}{h^2} =\cfrac{1}{9}\)
∴ \(\cfrac{1}{h^2} +\cfrac{1}{r^2} =\cfrac{1}{9}\) (Answer)