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docs/lib3x-angle_between.md

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+# angle_between
+
+Returns the angle between two vectors.
+
+**Since:** 3.0
+
+## Parameters
+
+- `vt1` : vector 1.
+- `vt2` : vector 2.
+
+## Examples
+
+    use <util/angle_between.scad>;
+
+    assert(angle_between([0, 1], [1, 0]) == 90);
+    assert(angle_between([0, 1, 0], [1, 0, 0]) == 90);
+    assert(round(angle_between([1, 1, 0], [1, 1, sqrt(2)])) == 45);