# HELP! how to plug this into the calculator sigma notation?

1. Aug 10, 2010

### femmed0ll

how would i plug this into the calculator? to find the sum?
step by step process? thankss!

4
∑ 2 cos (π/k)
k = 1

i tried this site
http://mathbits.com/mathbits/tisection/Algebra2/summation.htm [Broken]
and i got a different answer...so i just need help with the set up on a T.I calc.

Last edited by a moderator: May 4, 2017
2. Aug 10, 2010

### Staff: Mentor

Why would you want to? This is a summation with four terms. Just expand the summation into its four terms.

3. Aug 11, 2010

### HallsofIvy

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

Since $cos(\pi)= -1$, $cos(\pi/2)= 0$, $cos(\pi/3)= 1/2$, and $cos(\pi/4)= \sqrt{2}/2$, you shouldn't need to use a calculator.

4. Aug 12, 2010

### Coriolis314

for the function f(x) for x=a to x=b the screen should read

sum(seq(f(x),x,a,b,1)

you should be able to catalog or 2nd[math] to find the [sum(] and [seq(] operators

hope this helps