### Home > PC > Chapter 4 > Lesson 4.2.1 > Problem4-78

4-78.
1. Write each of the following expressions using sigma notation. Homework Help ✎

1. cos(2) + 2 cos(4) + 3 cos(6) + … + 15 cos(30)

$\displaystyle\sum\limits_{\textit{k}=0}^?\frac{1}{3+(?)\textit{k}}$

$\displaystyle\sum\limits_{\textit{k}=0}^?\sqrt{5+(?)\textit{k}}$

Use the same thinking process as (a) and (b) above.