Write the sum without sigma notation and evaluate it?

[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!

 

[adriank]

It's a finite sum...

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

...

 

[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)$with 1, 2, 3, and 4 and then add.$[/itex]