- #1

foo9008

- 678

- 4

## Homework Statement

we know that a2 , a4 ,a6 (even number ) = 0 , but when a1 , a3 , a5 (odd numbers) , the answer of an alternate between positive and negative ... in the second circle , the author represent it with (-1)^(n+1) , i don't think this is correct , this is because when n=3 , an =

**-**2/ 3pi when n=3 , [ (-1) ^(3+1 ) ] = positive 1 , not negative 1 ! can someone explain on this ?