diff --git a/slides/sections/1.md b/slides/sections/1.md
index 9c1c209..4552283 100644
--- a/slides/sections/1.md
+++ b/slides/sections/1.md
@@ -13,6 +13,19 @@ aspectratio: 169
 fontsize: 14pt
 mathfont: FiraMath-Regular
 sansfont: Fira Sans
+
+header-includes: |
+  ```{=latex}
+  % "thus" in formulas
+  \DeclareMathOperator{\thus}{%
+    \hspace{30pt} \Longrightarrow \hspace{30pt}
+  }
+
+  % "et" in formulas
+  \DeclareMathOperator{\et}{%
+  \hspace{30pt} \wedge \hspace{30pt}
+  }
+  ```
 ...
 
 # Landau distribution