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

[carlycakes]

how would i plug this into the calculator? to find the sum?
4
? 2 cos (?/k)
k = 1

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

 

[BigGlenntheHeavy]

Re: HELP! how to plug this into the calculator...sigma notat

\(\displaystyle On \ TI-89:\)

\(\displaystyle First, \ punch \ F3-4 \ to \ get \ your \ Epsilon.\)

\(\displaystyle Then \ 2 \ *(2nd)cos((2nd)\pi/(alpha \ k),alpha \ k,1,4) \\)

\(\displaystyle will \ give \ you: \ \sum_{k=1}^{4}2cos(\pi/k) \ = \ \sqrt2-1\)

 

[galactus]

Re: HELP! how to plug this into the calculator...sigma notat

Here's a screen capture from my Voyage 200. You probably have a TI-83?.

I inadvertently left out the 2, but that's just a thing.

 

[carlycakes]

Re: HELP! how to plug this into the calculator...sigma notat

umm i have a ti-84...
what exactly do i enter?

 

[BigGlenntheHeavy]

Re: HELP! how to plug this into the calculator...sigma notat

\(\displaystyle I'm \ not \ sure, \ but \ there \ shouldn't \ be \ that \ much \ difference \ between \ a \ TI-89 \ and\)

\(\displaystyle a \ TI-84.\)

\(\displaystyle Note: \ If \ everything \ else \ fails, \ look \ in \ the \ manual \ that \ came \ with \ your \ TI.\)

\(\displaystyle If \ you \ don't \ have \ one \ (a \ manual) \ write \ them \ and \ they'll \ be \ happy \ to \ send \ you \ one.\)

\(\displaystyle For \ my \ part \ (TI-89 \ user) \ I \ constantly \ find \ shortcuts, \ etc., \ using \ my \ manual.\)

 

[mmm4444bot]

The examples above do not apply to the TI-84 because the TI-84 is quite different.

(The TI-89 and the Voyage 200 both contain a Computer Algebra System; the TI-84 does not.)

Click HERE to download and save the TI-84 manual.

On page 182, I find the following example.

[attachment=0:ztpd3xr1]ti84.JPG[/attachment:ztpd3xr1]

This shows a nested command; the inner command seq() creates the sequence of elements, and the outer command sum() adds them together. Follow the syntax exactly as shown.

Of course, you will replace the expression 2^(N-1) with the expression 2cos(?/N).

To get the sum() and seq() commands, use the Catalog. (From the Catalog, you can paste any TI-84 command.)

Press [2ND] then [CATALOG] to display the command list. You can then scroll to the command that you want (or hit the key, to jump directly to the S's). Once the item you want is highlighted, hit enter to paste.

I hope this helps.