start point cube and cubeRoot operation

src/main/c/Calculator/calculator.c

@@ -19,6 +19,8 @@ double permutation(int n, int r);
 double combination(int n, int r);
 double factorial(double num);
 double power(double base, double exponent);
+double cube(double num);
+double cubeRoot(double num);
 
 int main() {
     double choice, num1, num2, result, angle;