Having trouble understanding Odd or even functions of Fourier

1. Jun 22, 2014

Spoolx

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

Is the function even, odd, or neither

$$y(t) = \frac{2At}{w} for 0<t<\frac{w}{2}$$
$$y(t) = \frac{-2At}{w}+2A for \frac{w}{2}<t<w$$

2. Relevant equations

even function f(-t) = f(t)
off function f(-t) = -f(t)

3. The attempt at a solution

I just dont understand the concept, any help is appreciated.

2. Jun 22, 2014

SteamKing

Staff Emeritus
An example of a even function is y = cosine (x) or y = x^2.
An example of an odd function is y = sine (x) or y = x.

If you look a graphs of these functions, what property of their graphs distinguishes an even function from an odd function?

3. Jun 22, 2014

vela

Staff Emeritus
I believe you meant to specify one piecewise function:
$$y(t) = \begin{cases} \frac{2At}{w}, & 0 \le t < \frac w2 \\ 2A - \frac{2At}{w}, & \frac w2 \le t < w \end{cases}.$$ This specifies just one period of the function. You want to repeat it so that you have a function defined for all $t$. The question is asking if the resulting function is even, odd, or neither.

4. Jun 22, 2014

Spoolx

That is correct, I could not figure out how to do the piecewise function.

I have done a bunch of reading and I still dont get it. If i graph it (see attachment it doesnt appear to be symmetrical about either axis, or maybe I am just missing something)

Thanks

Attached Files:

• Untitled.png
File size:
1.3 KB
Views:
73
Last edited: Jun 22, 2014
5. Jun 22, 2014

LCKurtz

What you have drawn is just one period. Draw some more of the graph, using the fact that you know what a period looks like, going both directions and see if what you get looks even or odd.

6. Jun 22, 2014

Spoolx

in that case I would say its symmetrical about the y axis which I believe is like a cos function so even?

7. Jun 22, 2014

LCKurtz

Yes. You can see from the graph that $f(-x)=f(x)$.

8. Jun 23, 2014

Spoolx

Well I thought I understood it, but I ran into two more problems which dont make sense

To me, they both should be Cos or even functions but the book says the first one is an odd function.

What am I missing?

Thanks so much

Attached Files:

• untitled.bmp
File size:
477 KB
Views:
80
9. Jun 23, 2014

benorin

If u look at the functions, they both have a factor of t, so they are like sin(t) or just t, odd.

10. Jun 23, 2014

LCKurtz

No benorin, that is not correct at all.

@Spoolx: Generally you should start a new thread with a new question. If you extend those functions by drawing more periods as you did before you will wind up with one of three possibilities: even, odd, or neither. Ignoring the book's answer, tell us what you think and why.