Closing #14

src/2_coordinates.md

@@ -306,7 +306,7 @@ The relation between Cartesian and spherical coordinates is defined by:
 
 The inverse transformation is easy to find: 
 !!! info "The inverse relation between Cartesian and spherical coordinates"
-    $$r = \sqrt{x^2+y^2+z^2}, \qquad $r \in \left<0, \infty \right)$$$
+    $$r = \sqrt{x^2+y^2+z^2}, \qquad r \in \left<0, \infty \right)$$
     $$\varphi = \begin{cases} \arctan(y/x) &{\rm for ~} x>0; \\
     \pi + \arctan(y/x) & {\rm for ~} x<0 {\rm ~ and ~} y>0;\\
     -\pi + \arctan(y/x) &{\rm for ~} x<0 {\rm ~ and ~} y<0.