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 CAS fourier_an ...
17-01-2016, 02:38 PM
Post: #1
 REF Junior Member  Posts: 3 Joined: Jan 2016 Reputation: 0
CAS fourier_an ...
Hello friends,

I try to use the new Funktion "fourier_an", "..._bn" or "..._cn" on CAS.
The function I try to approximate is a rectangle signal.

T=10ms
f(x)= 10V = û
a=0
n=1...6

In CAS: fourier_bn(Expr,Var,T,n,a)
so I type fourier_bn(10,x,10,1,0) for b1

Normally the result is:
b1=û*2/PI=20/PI
b2=0
b3=û*2/(3*PI)=20/(3*PI)
b4=0
b5=û*2/(5*PI)=20/(5*PI)
b6=0
a0=û/2=5

But with HP Prime calculator:
b1=b2=b3=b4=b5=b6=0
a0=10
The results are compleately wrong!!!

Is there a mistake in using the function on my side or is it an bug?

REF
18-01-2016, 06:06 PM
Post: #2
 JMB Junior Member  Posts: 8 Joined: Nov 2015 Reputation: 0
RE: CAS fourier_an ...
Hi!

I assume that your function has a value of 10 V for the first 10 ms, and 0 V for the next 10 ms; in that case the period is 20 ms.

So, if you use fourier_an() and fourier_bn() with a function whose value is: 10 if x<10, and 0 if x>=10, and use 20 as the period, you'll get the correct answer.

a0=5
b1=20/PI
b2=0
b3=20/(3*PI)
...
13-04-2016, 09:43 PM
Post: #3
 REF Junior Member  Posts: 3 Joined: Jan 2016 Reputation: 0
RE: CAS fourier_an ...
Can you show me how to type in?

fourier_an(10,x,20,0,0)
fourier_bn(10,x,20,1,0)
.
.
.

Is this right?

REF

(18-01-2016 06:06 PM)JMB Wrote:  Hi!

I assume that your function has a value of 10 V for the first 10 ms, and 0 V for the next 10 ms; in that case the period is 20 ms.

So, if you use fourier_an() and fourier_bn() with a function whose value is: 10 if x<10, and 0 if x>=10, and use 20 as the period, you'll get the correct answer.

a0=5
b1=20/PI
b2=0
b3=20/(3*PI)
...
29-04-2016, 05:46 PM (This post was last modified: 01-05-2016 11:49 AM by JMB.)
Post: #4
 JMB Junior Member  Posts: 8 Joined: Nov 2015 Reputation: 0
RE: CAS fourier_an ...
Please see the following screen capture: The function: 10 if x<10, 0 if x >=10 is entered by pressing the template key, and then selecting the 5th icon of the 1st row: 27-09-2016, 09:14 PM
Post: #5
 REF Junior Member  Posts: 3 Joined: Jan 2016 Reputation: 0
RE: CAS fourier_an ...
(29-04-2016 05:46 PM)JMB Wrote:  Please see the following screen capture:

The function: 10 if x<10, 0 if x >=10 is entered by pressing the template key, and then selecting the 5th icon of the 1st row:

Thank you very much!!! It works fine. :-)
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