diff --git a/cheatsheet.md b/cheatsheet.md
index 8162a80c..1e855159 100644
--- a/cheatsheet.md
+++ b/cheatsheet.md
@@ -1,7 +1,15 @@
-2d math
+## math
 
-https://www.arndt-bruenner.de/mathe/scripts/dreiecksberechnungrw.htm
+$π = radians(180.0) = acos(0.0) * 2.0$
+
+#### rule of three
+
+$\frac{x1}{x2} = \frac{?}{y2}$ -> $? = \frac{x1 * y2}{x2}$
+
+### 2d math
 
+
+### trigonometry
 ```
                                       _- \
 sin(α) = a / c                     _-   . \
@@ -11,3 +19,7 @@ sin(β) = b / c            _-  α            β \
 cos(β) = a / c           ----------------------
 tan(β) = b / a                     c
 ```
+
+https://www.arndt-bruenner.de/mathe/scripts/dreiecksberechnungrw.htm
+
+### 3d math