diff --git a/src/exponent.c b/src/exponent.c
index bbe2221..8909d56 100644
--- a/src/exponent.c
+++ b/src/exponent.c
@@ -4,6 +4,7 @@
 
 #include "exponent.h"
 #include "logarithmus.h"
+#include "reihen.h"
 
 double absD(double x){
     if(x<0){
@@ -49,24 +50,3 @@ double powerD(double exp, double base){
     return -1.0;
 }
 
-unsigned long long fac(int x){
-    unsigned long long prod = 1;
-    if(x==0) return 1;
-    for (int i = 1; i <= x; i++){
-        if (prod > ULLONG_MAX / i){
-            break;
-        }
-        prod*=i;
-    }
-    return prod;
-}
-
-
-double exponential(double x){
-    double sum = 0.0;
-    for(int i = 0; i<=21; i++){
-        sum += (1.0/fac(i)*(powerD(i,x)));
-    }
-    return sum;
-}
-
diff --git a/src/exponent.h b/src/exponent.h
index 9b53200..1264177 100644
--- a/src/exponent.h
+++ b/src/exponent.h
@@ -3,7 +3,6 @@
 
 double p(double exp, double base);
 double powerD(double exp, double base);
-double exponential(double x);
 double absD(double x);
 
 #endif // exponent.h
\ No newline at end of file
diff --git a/src/logarithmus.c b/src/logarithmus.c
index 1c613e5..fa6ea62 100644
--- a/src/logarithmus.c
+++ b/src/logarithmus.c
@@ -3,6 +3,7 @@
 
 #include "logarithmus.h"
 #include "exponent.h"
+#include "reihen.h"
 
 double logX(double base, double value){
     if(base == 1.0 || base <= 0.0 || value <= 0.0){
diff --git a/src/reihen.c b/src/reihen.c
index cd80bc3..01fd0a5 100644
--- a/src/reihen.c
+++ b/src/reihen.c
@@ -4,4 +4,24 @@
 
 #include "reihen.h"
 #include "exponent.h"
-#include "logarithmus.h"
\ No newline at end of file
+#include "logarithmus.h"
+
+unsigned long long fac(int x){
+    unsigned long long prod = 1;
+    if(x==0) return 1;
+    for (int i = 1; i <= x; i++){
+        if (prod > ULLONG_MAX / i){
+            break;
+        }
+        prod*=i;
+    }
+    return prod;
+}
+
+double exponential(double x){
+    double sum = 0.0;
+    for(int i = 0; i<=21; i++){
+        sum += (1.0/fac(i)*(powerD(i,x)));
+    }
+    return sum;
+}
\ No newline at end of file
diff --git a/src/reihen.h b/src/reihen.h
index bb17ea0..bd4e520 100644
--- a/src/reihen.h
+++ b/src/reihen.h
@@ -1,6 +1,6 @@
 #ifndef REIHEN_H
 #define REIHEN_H
 
-
+double exponential(double x);
 
 #endif // reihen.h
\ No newline at end of file
diff --git a/test/test_exponent.c b/test/test_exponent.c
index ae49c01..d137507 100644
--- a/test/test_exponent.c
+++ b/test/test_exponent.c
@@ -4,6 +4,7 @@
 
 #include "exponent.h"
 #include "logarithmus.h"
+#include "reihen.h"
 
 void setUp(void)
 {
@@ -101,26 +102,4 @@ void test_exponent_edge_case(void){
     TEST_ASSERT_DOUBLE_WITHIN(0.0001, -1.0, r5);
 }
 
-void test_Exponent_with_positive_number(void){
-    double r1, r2, r3;
-
-    r1 = exponential(0.0);
-    r2 = exponential(1.0);
-    r3 = exponential(2.0);
-
-    TEST_ASSERT_EQUAL_DOUBLE(1.0, r1);
-    TEST_ASSERT_DOUBLE_WITHIN(0.0001, 2.718282, r2);
-    TEST_ASSERT_DOUBLE_WITHIN(0.0001, 7.389056, r3);
-}
-
-void test_Exponent_with_negative_number(void){
-    double r1, r2, r3;
-
-    r1 = exponential(-1.0);
-    r2 = exponential(-2.0);
-
-    TEST_ASSERT_DOUBLE_WITHIN(0.000001, 0.367879, r1);
-    TEST_ASSERT_DOUBLE_WITHIN(0.000001, 0.135335, r2);
-}
-
 #endif // TEST
\ No newline at end of file
diff --git a/test/test_logarithmus.c b/test/test_logarithmus.c
index 0f7aba1..7c24c13 100644
--- a/test/test_logarithmus.c
+++ b/test/test_logarithmus.c
@@ -4,6 +4,7 @@
 
 #include "logarithmus.h"
 #include "exponent.h"
+#include "reihen.h"
 
 void setUp(void)
 {
diff --git a/test/test_reihen.c b/test/test_reihen.c
index 043fc95..13d490c 100644
--- a/test/test_reihen.c
+++ b/test/test_reihen.c
@@ -14,4 +14,26 @@ void tearDown(void)
 {
 }
 
+void test_Exponent_with_positive_number(void){
+    double r1, r2, r3;
+
+    r1 = exponential(0.0);
+    r2 = exponential(1.0);
+    r3 = exponential(2.0);
+
+    TEST_ASSERT_EQUAL_DOUBLE(1.0, r1);
+    TEST_ASSERT_DOUBLE_WITHIN(0.0001, 2.718282, r2);
+    TEST_ASSERT_DOUBLE_WITHIN(0.0001, 7.389056, r3);
+}
+
+void test_Exponent_with_negative_number(void){
+    double r1, r2, r3;
+
+    r1 = exponential(-1.0);
+    r2 = exponential(-2.0);
+
+    TEST_ASSERT_DOUBLE_WITHIN(0.000001, 0.367879, r1);
+    TEST_ASSERT_DOUBLE_WITHIN(0.000001, 0.135335, r2);
+}
+
 #endif // TEST
\ No newline at end of file