add doc

README.md

@@ -355,8 +355,8 @@ These examples incubate dotSCAD and dotSCAD refactors these examples. See [examp
 
  Signature | Description
 --|--
-**triangle/tri_circumcenter**(shape_pts) | return the circumcenter of a triangle.
+[**triangle/tri_circumcenter**(shape_pts)](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_circumcenter.html) | return the circumcenter of a triangle.
-**triangle/tri_incenter**(shape_pts) | return the incenter of a triangle.
+[**triangle/tri_incenter**(shape_pts)](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_incenter.html) | return the incenter of a triangle.
 **triangle/tri_ear_clipping**(shape_pts,  ret = "TRI_INDICES", ...) |  triangulation by [ear clipping](https://en.wikipedia.org/wiki/Polygon_triangulation#Ear_clipping_method).
 **triangle/tri_delaunay**(points, ret = "TRI_INDICES") | return the [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation) of the points.
 **triangle/tri_delaunay_indices**(d) | return triangle indices from a delaunay object.

docs/lib3x-tri_circumcenter.md

@@ -0,0 +1,15 @@
+# tri_circumcenter
+
+The `tri_circumcenter` function returns the circumcenter of a 2D triangle. 
+
+**Since:** 3.1
+
+## Parameters
+
+- `shape_pts` : the vertices of a 2D triangle.
+
+## Examples
+
+    use <triangle/tri_circumcenter.scad>;
+   
+    assert(tri_circumcenter([[0, 0], [10, 20], [15, 10]]) == [3.75, 10.625]);

docs/lib3x-tri_incenter.md

@@ -0,0 +1,15 @@
+# tri_incenter
+
+The `tri_incenter` function returns the incenter of a 2D triangle. 
+
+**Since:** 3.1
+
+## Parameters
+
+- `shape_pts` : the vertices of a 2D triangle.
+
+## Examples
+
+    use <triangle/tri_incenter.scad>;
+   
+    assert(tri_incenter([[0, 0], [15, 0], [0, 20]]) ==  [5, 5]);

src/triangle/tri_circumcenter.scad

@@ -1,3 +1,13 @@
+/**
+* tri_circumcenter.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_circumcenter.html
+*
+**/
+
 function tri_circumcenter(shape_pts) =
    let(
       p0 = shape_pts[0],

src/triangle/tri_incenter.scad

@@ -1,3 +1,13 @@
+/**
+* tri_incenter.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_incenter.html
+*
+**/
+
 function tri_incenter(shape_pts) = 
     let(
         pa = shape_pts[0],