Added logarithm function for base 10 logarithmic calculations

src/main/c/main_taschenrechner.c

@@ -39,8 +39,15 @@ double tangentFunction(double angle) {
     return tan(angle * M_PI / 180.0);
 }
 
-// scientificmode
+// Logarithmic functions
+double logarithmFunction(double x) {
+    // Logarithm with base 10
+    return log10(x);
+}
+ 
 
+
+// scientificmode
 int scientificMode(){
 
     double num, result;

src/main/c/taschenrechner.h

@@ -15,6 +15,8 @@ double cosineFunction(double angle);
 
 double tangentFunction(double angle);
 
+double logarithmFunction(double x);
+
 int mode(int userChoice);
 
 int displayMenu();