計量テンソル
( x 1 , x 2 , x 3 ) = ( r , θ , z ) {\displaystyle (x^{1},x^{2},x^{3})=(r,\theta ,z)\ }
g = [ 1 0 0 0 ( x 1 ) 2 0 0 0 1 ] , d s 2 = ( d r ) 2 + r 2 ( d θ ) 2 + ( d z ) 2 {\displaystyle g={\begin{bmatrix}1&0&0\\0&(x^{1})^{2}&0\\0&0&1\end{bmatrix}},\quad ds_{}^{2}=(dr)^{2}+r^{2}(d\theta )^{2}+(dz)^{2}}