Nth Term Formula Sequence

  • #1

Homework Statement


I am trying to solve this problem and need help with one aspect.


Homework Equations


sequence: 0,-1,0,1 -- repeated.


The Attempt at a Solution


How do I make every 4th term of the sequence a negative number?

for instance i have: (1 + (-1)^n)/2 but i don't know how to alternative the -1 term in.
 
Last edited:

Answers and Replies

  • #2
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,348
1,022

Homework Statement


I am trying to solve this problem and need help with one aspect.

Homework Equations


sequence: 0,-1,0,1 -- repeated.

The Attempt at a Solution


How do I make every 4th term of the sequence a negative number?

for instance i have: (1 + (-1)^n)/2 but i don't know how to alternative the -1 term in.
What functions are you willing to use.

This can easily be done with sine or cosine .

You can probably come up with some solution using the "mod" function.
 
  • #3
please explain how i would implement cosine or sine.
 
  • #4
Try sin (n*pi/2) and add integer constants to n to shift the series.
 
  • #5
then you are going 1, 0, -1, 0. (so if i put sin(pi/2 + npi/2) into the ratio, then i multiply by negative 1 the correct number of times, but what about the zeros? sinx=0 ---> v(sinx) = 0
 
  • #6
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,348
1,022
then you are going 1, 0, -1, 0. (so if i put sin(pi/2 + npi/2) into the ratio, then i multiply by negative 1 the correct number of times, but what about the zeros? sinx=0 ---> v(sinx) = 0
So, it appears you're starting with n = 1 .

Why is it that you say that [itex]\displaystyle \ -\,\sin\left(\frac{\pi}{2}+\frac{n\pi}{2}\right)\ [/itex] doesn't work ?
 

Related Threads on Nth Term Formula Sequence

Replies
5
Views
777
Replies
2
Views
1K
Replies
6
Views
2K
  • Last Post
Replies
20
Views
5K
  • Last Post
Replies
7
Views
8K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
2
Views
3K
Replies
11
Views
9K
  • Last Post
Replies
6
Views
985
  • Last Post
Replies
11
Views
2K
Top