### Home > PC > Chapter 6 > Lesson 6.3.1 > Problem6-115

6-115.
1. Rewrite each of the following series using summation notation. Homework Help ✎

1. cos(1.2) + cos(1.5) + cos(1.8) + … + cos(3.9)

2. 1 − 3 + 5 − 7 + 9 − 11 + … + 201

$\sum_{k=0}^{\text{terms}-1}\text{cos(pattern)}$

What expression would change the sign back and forth (+ to −)?

(−1)n
n is an integer.

What expression gives odd numbers?

2n + 1