Let $\mu(x)dx$ be a mesuremeasure in $\mathbb{R}^{2n-2}$, where $\mu$ ( a $C^\infty$ and positive function) beis the density of the volume in the sense that $Vol_\mu(B_r)=\int_{B_r}\mu(x)dx$$\DeclareMathOperator{\Vol}{\mathrm{Vol}} \Vol_\mu(B_r)=\int_{B_r}\mu(x)dx$, where $B_r$ be the ball of raduceradius $r$ on $\mathbb{R}^{2n-2}$ . weNow suppose that $\mu(x)dx=d\Gamma$, By stockes: by Stokes's theorem we get$$Vol_\mu(B_r)=\int_{B_r}\mu(x)dx=\int_{B_r}d\Gamma=\int_{S_r}\Gamma$$ $$\Vol_\mu(B_r)=\int_{B_r}\mu(x)dx=\int_{B_r}d\Gamma=\int_{S_r}\Gamma$$ where $S_t$ beis the sphere in $\mathbb{R}^{2n-3}$ the question is. The question is: can we explainexpress the area of $S_r$ as a function of the density $\mu$?