> **Possible Duplicate:**  
> [How to express $ds$?(when we know expression for $ds^{2}$)](http://physics.stackexchange.com/questions/45768/how-to-express-dswhen-we-know-expression-for-ds2)  

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Is this General relativistic action correct?

$\mathcal S =-Mc \int ds = \int_{\xi_0}^{\xi_1}\sqrt{g_{\mu\nu}(x)\frac{dx^\mu(\xi)}{d\xi} \frac{dx^\nu(\xi)}{d\xi}} \ \ d\xi $