Update src/2_coordinates.md

src/2_coordinates.md

@@ -305,12 +305,15 @@ The inverse transformation is easy to find:
     $$\theta = \arccos(z/\sqrt{x^2+y^2+z^2})$$
     $$\phi = \begin{cases} \arctan(y/x) &{\rm for ~} x>0; \\
     \pi + \arctan(y/x) & {\rm for ~} x<0 {\rm ~ and ~} y>0;\\
-    -\pi + \arctan(y/x) &{\rm ~ for ~} x<0 {\rm ~ and ~} y<0.
+    -\pi + \arctan(y/x) &{\rm for ~} x<0 {\rm ~ and ~} y<0.
     \end{cases}$$ 
     
 These relations can be derived from the following figure:
 
-![image](figures/Coordinates_17_0.svg)
+<figure markdown>
+  ![image](figures/Coordinates_17_0.svg)
+  <figcaption></figcaption>
+</figure>
 
 The distance related to a change in the spherical coordinates is
 calculated using Pythagoras’ theorem. The length $ds$ of a short segment
@@ -328,7 +331,11 @@ $$ds^2 = r^2 \left(\sin^2 \vartheta d\varphi^2 + d\vartheta^2\right) + dr^2.$$
 The picture below shows the geometry behind the calculation of this
 displacement.
 
-![image](figures/Coordinates_19_0.svg)
+<figure markdown>
+  ![image](figures/Coordinates_19_0.svg)
+  <figcaption></figcaption>
+</figure>
+
 
 From these arguments we can again also find the volume element, it is
 here given as