diff --git a/src/main/c/main_taschenrechner.c b/src/main/c/main_taschenrechner.c
index d99a933..20b7c33 100644
--- a/src/main/c/main_taschenrechner.c
+++ b/src/main/c/main_taschenrechner.c
@@ -34,6 +34,10 @@ double cosineFunction(double angle) {
     return cos(angle * M_PI / 180.0);
 }
 
+double tangentFunction(double angle) {
+    // Convert degrees to radians for trigonometric functions
+    return tan(angle * M_PI / 180.0);
+}
 
 // scientificmode
 
diff --git a/src/main/c/taschenrechner.h b/src/main/c/taschenrechner.h
index a5b9d40..a2b16d0 100644
--- a/src/main/c/taschenrechner.h
+++ b/src/main/c/taschenrechner.h
@@ -13,6 +13,8 @@ double sineFunction(double angle);
 
 double cosineFunction(double angle);
 
+double tangentFunction(double angle);
+
 int mode(int userChoice);
 
 int displayMenu();