diff --git a/constants.scad b/constants.scad
new file mode 100644
index 0000000..1ad2992
--- /dev/null
+++ b/constants.scad
@@ -0,0 +1,6 @@
+TAU = 6.2831853071; //2*PI, see http://tauday.com/
+PI = TAU/2;
+
+// translates a imperial measurement in inches to meters
+mm_per_inch = 25.4;
+
diff --git a/math.scad b/math.scad
index ca1f211..19c3dd9 100644
--- a/math.scad
+++ b/math.scad
@@ -1,4 +1,4 @@
-PI = 3.14159;
+include <constants.scad>
+
+function deg(angle) = 360*angle/TAU;
 
-// translates a imperial measurement in inches to meters
-mm_per_inche =25.4;