Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Problem with sinus

  1. Jan 12, 2009 #1
    problem with sinus :)

    1. The problem statement, all variables and given/known data

    Hey guys.
    cos(n*x) when n is natural and x=pi equals to (-1)^n as I wrote in the pic.
    What I'm looking for is the same thing in sinus, lets say again that n is natural, is there a x that can make sinus to behave something like cos? and by that I mean an expression that can be written in on line like (-1)^n (x can be anything).
    I hope that was understood.
    Thanks in advance.

    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

    • 1.jpg
      1.jpg
      File size:
      4.5 KB
      Views:
      74
  2. jcsd
  3. Jan 12, 2009 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Re: problem with sinus :)

    Like sin(n*pi+pi/2)=(-1)^n?
     
  4. Jan 13, 2009 #3
    Re: problem with sinus :)

    That's the idea except that I have the expression (nx) inside the sinus and from that I cant get n*pi+pi/2 (x can not be depended in n).
    lets say x=pi/2, is there a way to write the result in one line? like cos(n*pi) = (-1)^n.
     
  5. Jan 13, 2009 #4

    Borek

    User Avatar

    Staff: Mentor

    Re: problem with sinus :)

    sin(n*pi/2)? For any integer n? Is that what you are asking for?

    If so, it is even simpler than cos. Take a look at sin plot.
     
  6. Jan 13, 2009 #5

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Re: problem with sinus :)

    Then how about sin(n*pi)=0?
     
  7. Jan 13, 2009 #6

    Borek

    User Avatar

    Staff: Mentor

    Re: problem with sinus :)

    sin(n*pi)... that's what I meant :grumpy:

    Combining sinus problem with sinuses problems is a sure way of getting headache.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook