python练习时出现了报错怎么改

Question

 

望指出错误

Answer 1

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

sum = 0
n = int(input('输入该表达式的项数： '))
for i in range(1,n+1):
    sum += pow((-1),(i+1))/(i*2-1)

print(round(sum,2))