# Homework Help: Write the sum without sigma notation and evaluate it?

1. Aug 9, 2010

### femmed0ll

4
∑ 2cos (π/k)
k = 1

i have the answer..but all i need it the steps on how to figure it out!
thanks!

2. Aug 9, 2010

It's a finite sum...

$$\sum_{k=1}^4 2 \cos(\pi/k) = 2 \cos(\pi/1) + 2 \cos(\pi/2) + 2 \cos(\pi/3) + 2 \cos(\pi/4)$$

...

3. Aug 9, 2010

### HallsofIvy

It is not a question of "figuring it out", it is just a question of knowing what that notation means.

It means exactly what adriank said: replace the "k" in [itex]cos(\pi/k)[itex] with 1, 2, 3, and 4 and then add.