diff --git a/src/__comm__/__edge_r.scad b/src/__comm__/__edge_r.scad
index 64ace0dc..c6492498 100644
--- a/src/__comm__/__edge_r.scad
+++ b/src/__comm__/__edge_r.scad
@@ -1,5 +1,7 @@
 function __edge_r_begin(orig_r, a, a_step, m) =
-    (orig_r * cos(a_step / 2)) / cos((m - 0.5) * a_step - a);
+    let(half_a_step = a_step / 2)
+    orig_r * cos(half_a_step) / cos(m * a_step - half_a_step - a);
 
-function __edge_r_end(orig_r, a, a_step, n) =      
-    (orig_r * cos(a_step / 2)) / cos((n + 0.5) * a_step - a);
\ No newline at end of file
+function __edge_r_end(orig_r, a, a_step, n) =    
+    let(half_a_step = a_step / 2)  
+    orig_r * cos(half_a_step) / cos(n * a_step + half_a_step  - a);
\ No newline at end of file