add math basic tut

Author: luisaFelixSalles

doc/source/user_guide/index.rst

@@ -70,6 +70,7 @@ Troubleshooting
     tutorials/distributed_files/index.rst
     tutorials/dpf_server/index.rst
     tutorials/licensing/index.rst
+    tutorials/mathematics/index.rst
 
 .. toctree::
    :maxdepth: 2