diff --git a/src/trig_functions/.gitkeep b/src/trig_functions/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/src/trig_functions/trig_functions.c b/src/trig_functions/trig_functions.c
new file mode 100644
index 0000000..186a4fe
--- /dev/null
+++ b/src/trig_functions/trig_functions.c
@@ -0,0 +1,17 @@
+#include "trig_functions.h"
+#include <math.h>
+
+double calculate_sin(double angle) {
+    if (angle==0) return 0;
+    else return sin(angle);
+}
+
+double calculate_cos(double angle) {
+    if (angle==0) return 1;
+    else return cos(angle);
+}
+
+double calculate_tan(double angle) {
+    if (angle==0) return 0;
+    else return tan(angle);
+}
diff --git a/src/trig_functions/trig_functions.h b/src/trig_functions/trig_functions.h
new file mode 100644
index 0000000..e15575b
--- /dev/null
+++ b/src/trig_functions/trig_functions.h
@@ -0,0 +1,9 @@
+#ifndef trig_functions_H
+#define trig_functions_H
+
+double calculate_sin(double angle);
+double calculate_cos(double angle);
+double calculate_tan(double angle);
+
+#endif
+
diff --git a/test/trig_functions/.gitkeep b/test/trig_functions/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/test/trig_functions/test_trig_functions.c b/test/trig_functions/test_trig_functions.c
new file mode 100644
index 0000000..115d0c9
--- /dev/null
+++ b/test/trig_functions/test_trig_functions.c
@@ -0,0 +1,31 @@
+#include "unity.h"
+#include "trig_functions.h"
+#define PI 3.14159265
+
+void setUp(void){}
+
+void tearDown(void){}
+
+void test_sin() {
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_sin(0));
+    TEST_ASSERT_EQUAL_DOUBLE(1.0, calculate_sin(PI/2));
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_sin(PI));
+    TEST_ASSERT_EQUAL_DOUBLE(-1.0, calculate_sin(3*PI/2));
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_sin(2*PI));
+}
+
+void test_cos() {
+    TEST_ASSERT_EQUAL_DOUBLE(1.0, calculate_cos(0));
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_cos(PI/2));
+    TEST_ASSERT_EQUAL_DOUBLE(-1.0, calculate_cos(PI));
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_cos(3*PI/2));
+    TEST_ASSERT_EQUAL_DOUBLE(1.0, calculate_cos(2*PI));
+}
+
+void test_tan() {
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_tan(0));
+    TEST_ASSERT_EQUAL_DOUBLE(INFINITY, calculate_tan(PI/2)); // Tangens von 90 Grad ist unendlich
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_tan(PI));
+    TEST_ASSERT_EQUAL_DOUBLE(INFINITY, calculate_tan(3*PI/2)); // Tangens von 270 Grad ist unendlich
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, calculate_tan(2*PI));
+}