<img src="http://foxridge.mpiwg-berlin.mpg.de/permanent/einstein/annalen/Einst_Grund_de_1916/fulltext/img/Einst_Grund_de_19164x.png" alt="d X = sum a d x . n ns s s " class="math-display"/>
</center>
</td>
<td width="5%">(2)</td>
</tr>
</table>
<p class="nopar"/>
<p class="noindent">Setzt man diese Ausdrücke in (1) ein, so erhält man</p>
<table width="100%" class="equation">
<tr>
<td>
<a id="x1-4r3"/>
<center class="math-display">
<img src="http://foxridge.mpiwg-berlin.mpg.de/permanent/einstein/annalen/Einst_Grund_de_1916/fulltext/img/Einst_Grund_de_19165x.png" alt="ds2 = sum g dx dx , st s t st " class="math-display"/>