# Problem with sinus

1. Jan 12, 2009

### asi123

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.

2. Relevant equations

3. The attempt at a solution

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2. Jan 12, 2009

### Dick

Re: problem with sinus :)

Like sin(n*pi+pi/2)=(-1)^n?

3. Jan 13, 2009

### asi123

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.

4. Jan 13, 2009

### 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.

5. Jan 13, 2009

### Dick

Re: problem with sinus :)

6. Jan 13, 2009

### 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.