python中选用特定函数的相关问题

# -*- coding:utf-8 -*-

###题目一
def sumDigits(n):
    res = 0
    for i in str(n):
        res += int(i)
    return res

sumDigits(3456)


##题目二
def area(n,side):
    from math import tan, pi
    return ( n * pow(side,2) ) / ( 4 * tan(pi/4))


def main():
    n = int('输入正多边形的边数：')
    side = int('输入正多边形的边长：')
    res = area(n=n,side=side)

    print(res)


main()