fourier series of this function

Asked by HADIMARGO on 27 Jun 2019

Latest activity Commented on by HADIMARGO on 28 Jun 2019

4 views (last 30 days)

i want the fourier seris of function:

my code:

clear all
clc
syms x
f=(x+2).*(x>-2)-(x+2).*(x>-1)+(1).*(x<=1)-(1).*(x<=-1)+(2-x).*(x>1)-(2-x).*(x>=2);
N=10;
a_0=(1/pi)*int(f*cos(0*x),-pi,pi)
for n=1:N
    a_n(n)=(1/pi)*int(f*cos(n*x),-pi,pi);
    b_n(n)=(1/pi)*int(f*sin(n*x),-pi,pi);
end
a_n
b_n
 
f_new=a_0/2;
for n=1:N
    f_new=f_new+a_n(n)*cos(n*x)+b_n(n)*sin(n*x);
end
 
subs(f_new,x,5)
subs(f,x,5)

the error:

Error using symengine

Invalid integrand.

Error in sym/int (line 162)

rSym = mupadmex('symobj::intdef',f.s,x.s,a.s,b.s,options);

Error in Untitled3 (line 7)

a_0=(1/pi)*int(f*cos(0*x),-pi,pi)

my function:

2 Comments

infinity on 27 Jun 2019

Hello,

It is seen that the function "f" is not easy for Matlab to find it intergrand by using the fucntion "int". Maybe, you should try to split the piecewise function "f" into some small intervals, for example, [0, -2], [-2, -1], [-1, 1], .... Then, you can get the integral over these intervals.

HADIMARGO on 28 Jun 2019

i tryid but cannot find the correct code.

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