Chapter 12 Sequences and Series - 12.2 Analyze Arithmetic Sequences and Series - 12.2 Exercises - Problem Solving - Page 809: 68b

$l_n=2 \pi + (n-1) 0.0008 \pi$

Since, $l_n$ increases by $0.0008 \pi$ each term. We know that the general formula of an arithmetic sequence is given by $l_n= l_1+(n-1) d$ or, $l_n=2 \pi +(n-1) 0.0008 \pi$ Thus, we have $l_n=2 \pi + (n-1) 0.0008 \pi$