diff --git a/index.html b/index.html
index a24b5a6..ef1cbe6 100644
--- a/index.html
+++ b/index.html
@@ -39,8 +39,8 @@
 
         \[
             r = |x| \\
-            \phi = arctan(y/x) \\
-            \theta = arctan\left(\frac{\sqrt{x^2+y^2}}{z}\right)
+            \phi = \arctan(y/x) \\
+            \theta = \arctan\left(\frac{\sqrt{x^2+y^2}}{z}\right)
         \]
         </p>