diff --git a/egison.cabal b/egison.cabal
--- a/egison.cabal
+++ b/egison.cabal
@@ -1,5 +1,5 @@
 Name:                egison
-Version:             3.7.0
+Version:             3.7.1
 Synopsis:            Programming language with non-linear pattern-matching against non-free data
 Description:
   An interpreter for Egison, a **pattern-matching-oriented**, purely functional programming language.
diff --git a/lib/math/normalize.egi b/lib/math/normalize.egi
--- a/lib/math/normalize.egi
+++ b/lib/math/normalize.egi
@@ -21,7 +21,7 @@
    [rewrite-rule-for-rtu-poly 1#(contain-function? rtu %1)]
    [rewrite-rule-for-sqrt 1#(contain-function? sqrt %1)]
    [rewrite-rule-for-rt 1#(contain-function? rt %1)]
-;   [rewrite-rule-for-cos-and-sin 1#(or (contain-function-with-order? cos 2 %1) (contain-function-with-order? sin 2 %1))]
+   ;   [rewrite-rule-for-cos-and-sin 1#(or (contain-function-with-order? cos 2 %1) (contain-function-with-order? sin 2 %1))]
    [rewrite-rule-for-cos-to-sin 1#(contain-function-with-order? cos 2 %1)]
    })
 
@@ -77,7 +77,7 @@
 ;;
 
 (define $rewrite-rule-for-rtu
-  (compose 
+  (compose
            (map-terms rewrite-rule-for-rtu-term $)
            (map-polys rewrite-rule-for-rtu-poly $)
            ))
@@ -180,13 +180,13 @@
            (* ,a (,sin ,θ)^,2 ,mr)
            $pr)
         (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a mr)))]
-;       [(+ (* $a (,cos $θ)^,2 $mr)
-;           (* ,(* -1 a) (,sin ,θ)^,2 ,mr)
-;           $pr)
-;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (cos (* 2 θ)) mr)))]
-;       [(+ (* $a (,cos $θ) (,sin ,θ) $mr)
-;           $pr)
-;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' (/ a 2) (sin (* 2 θ)) mr)))]
+       ;       [(+ (* $a (,cos $θ)^,2 $mr)
+                   ;           (* ,(* -1 a) (,sin ,θ)^,2 ,mr)
+                   ;           $pr)
+                ;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (cos (* 2 θ)) mr)))]
+       ;       [(+ (* $a (,cos $θ) (,sin ,θ) $mr)
+                   ;           $pr)
+                ;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' (/ a 2) (sin (* 2 θ)) mr)))]
        [(+ (* $a $mr)
            (* ,(* -1 a) (,sin $θ)^,2 ,mr)
            $pr)
@@ -196,10 +196,10 @@
            $pr)
         (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (sin θ)^2 mr)))]
        ; (- 1 (cos (* 2 θ))) = (* 2 (sin θ)^2)
-;       [(+ (* $a $mr)
-;           (* ,(* -1 a) (,cos $θ) ,mr)
-;           $pr)
-;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' (* 2 a) (sin (/ θ 2))^2 mr)))]
+       ;       [(+ (* $a $mr)
+                   ;           (* ,(* -1 a) (,cos $θ) ,mr)
+                   ;           $pr)
+                ;        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' (* 2 a) (sin (/ θ 2))^2 mr)))]
        [_ poly]})))
 
 (define $rewrite-rule-for-cos-to-sin 1#(map-terms rewrite-rule-for-cos-to-sin-term' %1))
@@ -238,4 +238,4 @@
            $pr)
         (+ (* (+ a b) (`g args)^n mr)
            pr)]
-       [_ poly]})))
+              [_ poly]})))