Make the function signature less prominent, add an early example to docs

Signed-off-by: Nick Cameron <nrc@ncameron.org>

docs/kcl-std/functions/std-math-atan2.md

@@ -8,14 +8,16 @@ layout: manual
 Compute the four quadrant arctangent of Y and X.
 
 ```kcl
-atan2(
-  y: number(Length),
-  x: number(Length),
-): number(rad)
+sketch001 = startSketchOn(XZ)
+  |> startProfile(at = [0, 0])
+  |> angledLine(angle = atan2(y = 1.25, x = 2), length = 20)
+  |> yLine(endAbsolute = 0)
+  |> close()
+
+extrude001 = extrude(sketch001, length = 5)
+
 ```
 
-
-
 ### Arguments
 
 | Name | Type | Description | Required |
@@ -28,6 +30,15 @@ atan2(
 [`number(rad)`](/docs/kcl-std/types/std-types-number) - A number.
 
 
+### Function signature
+
+```kcl
+atan2(
+  y: number(Length),
+  x: number(Length),
+): number(rad)
+```
+
 ### Examples
 
 ```kcl