Nebo - P1 - Page 1

Greetings all!

I start with a couple of ideas about life!

  • what is life?
    In its simplest form, life is nothing more than a way of decreasing entropy in expanse of producing heat. Hence, it's just another way of contributing heat death of universe.
  • is it ok to live forever?
  • we loose the urgency of doing things. we will have always tomorrow, why to get up even? So we cant achive nothing.
  • even if we do things their value will drop by time. If given enough time you can
    achive anything.

Now, lets do some math
This is famous Parseval's theorem: if you expand a function in a complete orthtonormal set than their square's are related.

Complete set can be Fourier, Legendre, Bessel etc. This is very useful. It can be even used to define completeness. Let's see some example! first lets expand constant function f =1 in the interval 0 to 1 by sin functions

f(x)=n=1anun(x)an=baun(x)f(x)dxf2=h=1a2n
f=1un(x)=2×sin(nπx)an=102×sin(nπx)dx={0,neven2×2nπ,nodd
a2n={0,neven8n2π2,n0dd

thus Parseval's theorem tells us that

n=01(2n+1)2=1+132+152+=π28

Now, Here is a problem for you to repeat above
procedure.
function f and u are defined in interval-pi to pi

f(x)=12×π×eikxun(x)=12×π×einx12×π×eikx=n=-an12×π×einx

In this case using Parsevals' theorem show:

cosec2(πk)=1sin2(πk)=n=-1π2×(k-n)2

Comments

Popular posts from this blog

time dependent Schröidinger Equation

Introduction