How is the Sine Series Derived for Piecewise Functions?

  • Thread starter Thread starter hawaiidude
  • Start date Start date
  • Tags Tags
    Series Sine
Click For Summary
The discussion focuses on deriving the sine series for the piecewise function f(x) defined as 0 for x < 2 and 2 for x > 2, over the interval [0, 3]. The coefficients cn are calculated using integration, leading to a series representation involving sine functions. The final sine series expression incorporates terms that account for the discontinuity at x = 2, resulting in a combination of sine functions with specific coefficients. The confusion arises from the steps in the integration process and the evaluation of the series, but clarification is achieved through understanding the role of different n values in the sine series. The derivation illustrates the application of Fourier series to piecewise functions effectively.
hawaiidude
Messages
41
Reaction score
0
why is

the sine series for f(x) = { 0 x<2 on 0,3
2 x>2

L=3

cn=2/3 int b=3 and a =0 f(x) sin( nxpi/ L)dx
= 2/3 int. b=2 a=0 (0) sin( pi n x/ 3) dx + 2/3 int b=3 a =2 (2) sin n x pi/3 dx
= 0 + 4/3{-3n pi cos n pi x/3} x=3 and x=2 = 4/n pi { cos 2 n pi/3 - cos n pi }

f(x)=sigma n=1 4/n pi { cos 2n pi/3 -(-1)^n sin n pi x

cos 2 pi/3=-1/2...

f(x)=4/pi( 2/3 sin pix/3-3/4sin2 pi x/3 +2/3sin 3 pi x/3...

how did they get this? very confused
 
Last edited by a moderator:
Physics news on Phys.org
my guess would be differnt N values
 
ok never mind i get it now
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
28
Views
2K
  • · Replies 18 ·
Replies
18
Views
1K
Replies
18
Views
1K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 11 ·
Replies
11
Views
1K
  • · Replies 5 ·
Replies
5
Views
1K
Replies
8
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
8
Views
1K