1. Use a recursive function to implement x^n, and use the recycle sentences to implement n!.

2.Based on the function overloading, write four different functions with the same name max() that can be used to get the max values from two int arguments, two char arguments, two float arguments, and two double arguments. Then, test it with a main function in the program.

3. . Design a function display() with default arguments. The function can be used to display("where") when we input the string of "where", if we input no argument, the function will show "Hello".

4. Design a function Area(), when it is set as Area(10,30), it can calculate the area of sector with radius 10 and angle 30; when it is set as Area(10), it can calculate the area of a circle with radius 10.