diff --git a/egison.cabal b/egison.cabal
--- a/egison.cabal
+++ b/egison.cabal
@@ -1,5 +1,5 @@
 Name:                egison
-Version:             3.7.5
+Version:             3.7.6
 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
@@ -147,47 +147,47 @@
 (define $rewrite-rule-for-cos-and-sin-expr
   (lambda [$expr]
     (match [expr expr] [math-expr math-expr]
-      {[[<div (+ (* $a (,cos $慮) $mr)
+      {[[<div (+ (* $a (,cos $x) $mr)
                  $pr1)
               $pr2>
-         (| <div (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _) _>
-            <div _ (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _)>)]
-        (rewrite-rule-for-cos-and-sin-expr (/' (+' (*' a (-' (cos (/ 慮 2))^2 (sin (/ 慮 2))^2) mr) pr1) pr2))]
-       [[<div (+ (* $a (,sin $慮) $mr)
+         (| <div (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _) _>
+            <div _ (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _)>)]
+        (rewrite-rule-for-cos-and-sin-expr (/' (+' (*' a (-' (cos (/ x 2))^2 (sin (/ x 2))^2) mr) pr1) pr2))]
+       [[<div (+ (* $a (,sin $x) $mr)
                  $pr1)
               $pr2>
-         (| <div (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _) _>
-            <div _ (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _)>)]
-        (rewrite-rule-for-cos-and-sin-expr (/' (+' (*' (*' a 2) (*' (cos (/ 慮 2)) (sin (/ 慮 2))) mr) pr1) pr2))]
+         (| <div (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _) _>
+            <div _ (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _)>)]
+        (rewrite-rule-for-cos-and-sin-expr (/' (+' (*' (*' a 2) (*' (cos (/ x 2)) (sin (/ x 2))) mr) pr1) pr2))]
        [[<div $pr2
-              (+ (* $a (,cos $慮) $mr)
+              (+ (* $a (,cos $x) $mr)
                  $pr1)>
-         (| <div (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _) _>
-            <div _ (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _)>)]
-        (rewrite-rule-for-cos-and-sin-expr (/' pr2 (+' (*' a (-' (cos (/ 慮 2))^2 (sin (/ 慮 2))^2) mr) pr1)))]
+         (| <div (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _) _>
+            <div _ (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _)>)]
+        (rewrite-rule-for-cos-and-sin-expr (/' pr2 (+' (*' a (-' (cos (/ x 2))^2 (sin (/ x 2))^2) mr) pr1)))]
        [[<div $pr2
-              (+ (* $a (,sin $慮) $mr)
+              (+ (* $a (,sin $x) $mr)
                  $pr1)>
-         (| <div (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _) _>
-            <div _ (+ (* _ (| (,cos ,(/ 慮 2)) (,sin ,(/ 慮 2))) _) _)>)]
-        (rewrite-rule-for-cos-and-sin-expr (/' pr2 (+' (*' (*' a 2) (*' (cos (/ 慮 2)) (sin (/ 慮 2))) mr) pr1)))]
+         (| <div (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _) _>
+            <div _ (+ (* _ (| (,cos ,(/ x 2)) (,sin ,(/ x 2))) _) _)>)]
+        (rewrite-rule-for-cos-and-sin-expr (/' pr2 (+' (*' (*' a 2) (*' (cos (/ x 2)) (sin (/ x 2))) mr) pr1)))]
        [_ expr]})))
 
 (define $rewrite-rule-for-cos-and-sin-poly
   (lambda [$poly]
     (match poly math-expr
-      {[(+ (* $a (,cos $慮)^,2 $mr)
-           (* ,a (,sin ,慮)^,2 ,mr)
+      {[(+ (* $a (,cos $x)^,2 $mr)
+           (* ,a (,sin ,x)^,2 ,mr)
            $pr)
         (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a mr)))]
        [(+ (* $a $mr)
-           (* ,(* -1 a) (,sin $慮)^,2 ,mr)
+           (* ,(* -1 a) (,sin $x)^,2 ,mr)
            $pr)
-        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (cos 慮)^2 mr)))]
+        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (cos x)^2 mr)))]
        [(+ (* $a $mr)
-           (* ,(* -1 a) (,cos $慮)^,2 ,mr)
+           (* ,(* -1 a) (,cos $x)^,2 ,mr)
            $pr)
-        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (sin 慮)^2 mr)))]
+        (rewrite-rule-for-cos-and-sin-poly (+' pr (*' a (sin x)^2 mr)))]
        [_ poly]})))
 
 (define $rewrite-rule-for-cos-to-sin 1#(map-terms rewrite-rule-for-cos-to-sin-term' %1))
@@ -195,8 +195,8 @@
 (define $rewrite-rule-for-cos-to-sin-term'
   (lambda [$term]
     (match term math-expr
-      {[(* $a (,cos $θ)^,2 $mr)
-        (*' a (-' 1 (sin θ)^2) (rewrite-rule-for-cos-to-sin-term' mr))]
+      {[(* $a (,cos $x)^,2 $mr)
+        (*' a (-' 1 (sin x)^2) (rewrite-rule-for-cos-to-sin-term' mr))]
        [_ term]})))
 
 ;;
@@ -231,8 +231,8 @@
 (define $rewrite-rule-for-cos-to-sin-term'
   (lambda [$term]
     (match term math-expr
-      {[(* $a (,cos $θ)^,2 $mr)
-        (*' a (-' 1 (sin θ)^2) (rewrite-rule-for-cos-to-sin-term' mr))]
+      {[(* $a (,cos $x)^,2 $mr)
+        (*' a (-' 1 (sin x)^2) (rewrite-rule-for-cos-to-sin-term' mr))]
        [_ term]})))
 
 ;;
diff --git a/sample/graph.egi b/sample/graph.egi
--- a/sample/graph.egi
+++ b/sample/graph.egi
@@ -80,7 +80,6 @@
                    <cons <edge ,x_1 $x_i>
                          (loop $j [2 (- i 1)]
                            <cons <edge ,x_j ,x_i> ...>
-                           ...)
-                         _>
+                           ...)>
                    _)>
            x])))