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docs/lib-trim_shape.md

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+# trim_shape
+
+Given a tangled-edge shape. This function trims the shape to a non-tangled shape. It's intended to be a helper function after using `bijection_offset`. 
+
+**Since:** 1.3.
+
+## Parameters
+
+- `shape_pts` : The shape points.
+- `from` : The index of the start point you want to trim.
+- `to` : The index of the last point you want to trim.
+- `epsilon` : An upper bound on the relative error due to rounding in floating point arithmetic. Default to 0.0001.
+
+## Examples
+
+    include <hull_polyline2d.scad>;
+    include <trim_shape.scad>;
+    include <shape_taiwan.scad>;
+    include <bijection_offset.scad>;
+    include <midpt_smooth.scad>;
+
+    taiwan = shape_taiwan(50);
+    offseted = bijection_offset(taiwan, -2);
+    trimmed = trim_shape(offseted, 3, len(offseted) - 6);
+    smoothed = midpt_smooth(trimmed, 3);
+
+    #hull_polyline2d(taiwan, .1); 
+    %translate([25, 0, 0]) 
+        hull_polyline2d(offseted, .2);
+    hull_polyline2d(smoothed, .1); 
+
+![trim_shape](images/lib-trim_shape-1.JPG)
+