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

4-78.

Write each of the following expressions using sigma notation.

1. $\frac { 1 } { 3 } + \frac { 1 } { 3.5 } + \frac { 1 } { 4 } + \frac { 1 } { 4.5 } + \ldots + \frac { 1 } { 9.5 }$

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

2. $\sqrt { 5 } + \sqrt { 8 } + \sqrt { 11 } + \sqrt { 14 } + \ldots + \sqrt { 302 }$

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

3. $\text{cos}(2) + 2 \text{ cos}(4) + 3\text{ cos}(6) + … + 15\text{ cos}(30)$

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