refactoring: case(for logarithm and pow)

src/main/c/Calculator/calculator.c

@@ -84,6 +84,10 @@ double combination(int n, int r);
             return pow(num1, num2);
         case 6:
             return fmod(num1, num2);
+        case 7:
+            return log(num1);
+        case 8:
+            return pow(num1, num2);