# fourier series

Discussion in 'Homework Help' started by hamza324, Oct 18, 2011.

1. ### hamza324 Thread Starter Member

Jul 10, 2011
33
1
I am trying to solve fourier series problems. i have few confusions about that..

1) x(t) =$\sum c_x(k)e ^{jkwt}$

where as $c_x(k) = \int_T x(t) e^{-jwt} dt$

My question is that when which equation do we use to plot the graph.
and how do we take the values for the graph. Is it BODE PLOTS or is it simply plugging in the values.

suppose i havethis expression
$c_x(k)= A/2 \frac {cos(k\prod-1)}{k\prod}^2$

$or\ i\ have\ c_x(k)= A/2 \frac {sinc(k\prod-1)}{k\prod}^2$

then how can i graph this equation for $c_1\ ,\ c_2\ ,\ ......$

2. ### Georacer Moderator

Nov 25, 2009
5,151
1,268
Are these equations for $c_x(k)$ correct? The multiplication symbol has no argument in either of them. It refers to the product of what?

3. ### hamza324 Thread Starter Member

Jul 10, 2011
33
1
The question i have is f(t)= $A\ cos200\pi t$
and this is the expression for fourier series $x(t) = \sum^{+\infty}_{k=-\infty}c_ke^{j2wkt}$

i got the following solution for fourier coefficients

$now\ for\ c_k\ =-\frac{1}{4}\frac{Sin(\pi +k)(0.5)}{(\pi+k)}-\frac{1}{4}\frac{Sin(\pi - k)0.5}{\pi-k}-\frac{1}{4}\frac{Sin(\pi+k)1.5}{\pi+k}-\frac{1}{4}\frac{Sin(\pi-k)1.5}{\pi-k}$

Now my prof asks me to sketch the fourier series coefficients i.e. $c_k\ for\ k=\ 1,2,3,....$

I wanna know how to sketch the result i got