diff --git a/src/main/c/main_taschenrechner.c b/src/main/c/main_taschenrechner.c
index 60e57f1..f407180 100644
--- a/src/main/c/main_taschenrechner.c
+++ b/src/main/c/main_taschenrechner.c
@@ -22,6 +22,12 @@ int divide(int a, int b) {
     return a / b;
 }
 
+// Trigonometric functions
+double sineFunction(double angle) {
+    // Convert degrees to radians for trigonometric functions
+    return sin(angle * M_PI / 180.0);
+}
+
 
 // scientificmode
 
diff --git a/src/main/c/taschenrechner.h b/src/main/c/taschenrechner.h
index 5bbfe6b..1ca10c6 100644
--- a/src/main/c/taschenrechner.h
+++ b/src/main/c/taschenrechner.h
@@ -9,6 +9,8 @@ int multiply(int a, int b);
 
 int divide(int a, int b);
 
+double sineFunction(double angle);
+
 int mode(int userChoice);
 
 int displayMenu();