September 2017 Update

Task/Averages-Mean-angle/Scheme/averages-mean-angle.ss

@@ -0,0 +1,23 @@
+(import (srfi 1 lists))  ;; use 'fold' from library
+
+(define (average l)
+  (/ (fold + 0 l) (length l)))
+
+(define pi 3.14159265358979323846264338327950288419716939937510582097)
+
+(define (radians a)
+  (* pi 1/180 a))
+
+(define (degrees a)
+  (* 180 (/ 1 pi) a))
+
+(define (mean-angle angles)
+  (let* ((angles (map radians angles))
+         (cosines (map cos angles))
+         (sines (map sin angles)))
+    (degrees (atan (average sines) (average cosines)))))
+
+(for-each (lambda (angles)
+            (display "The mean angle of ") (display angles)
+            (display " is ") (display (mean-angle angles)) (newline))
+          '((350 10) (90 180 270 360) (10 20 30)))