Wow.. math forum? help me please..
-
come..
here is the questions..
First I get a sine wave:
x = sin(2*pi*10*(0:256:1.275))
I need a cube of x so... x = x*x*x
Ok, which is also equal to sin^3(x) right?
and I do a DFT.... discrete fourier transform...
So, N is the number of samples, 256...
k is the constant from the summation...
e is the exponential...
and n is the N increment...
This is the result...
The question is... Why I don't have a peak of 1? Since it is a RMS of 1v peak, I did an absolute(x)/N*2
And why there is 2 peak? My freqency is 10, the first peak is right, but why the other peak become 30?
Thanks in advance.. -
WAH..! Chim sia...see till eyes blurr..
hmmh hmm...i fail maths since small..soO cant help lo...
wahaha..
-
Wah.... WTH is this? F maths?????
-
Nvm -.-"Originally posted by Princess livia:
WAH..! Chim sia...see till eyes blurr..
hmmh hmm...i fail maths since small..soO cant help lo...
wahaha..
Lol... coz even some professors also can't explain
Hope which clever chap come help... 2 years free p-membership 
-
Engineering math..Originally posted by MohamedF:Wah.... WTH is this? F maths????? -
whoa, i never learn fourier transform before. and also why is x^3 equal to sin^3(x)? I dont get it I'm stupid.
-
That above is from DFT, discrete fourier transform...Originally posted by the.owl:whoa, i never learn fourier transform before. and also why is x^3 equal to sin^3(x)? I dont get it I'm stupid.
DFT uses summation instead of sine and cosine.
See this hierachy...
fourier series -> fourier transform -> discrete FT, continous FT
from DFT -> fast FT...
the sin^3(x) is from fourier series... which is:
sin(x)*sin(x)*sin(x) = sin(x^3)... -
I am waiting for CoolMyth to help me..
-
I am not versed in Engin Maths.
Wait for hisoka lah. -
Merry Meet MosPosterior,
E Maths. I have learnt & passed, completed my Engineering Studies long time ago. I have return the E Maths to Mother Earth. No time to help you also, better complete your work on your own, seek any help & clarifications from your Lecturer rather than asking those in the same situation as you are now. It won't help much also. Everyone have their ways of doing the sums & deriving answers be it orthodox method or not. Some may omit a few steps too, its best you try to understand them yourself & derive your own methods of countering such questions. Don't waste too much of your time doing nonsense.. better manage your time well, there is always a need for a time to play & time to study.
Blessed Be,
Oceanos -
i studied those before in year 2. gave back to lecturers liao.
-
haiz...sorry i can't help you as i've not learn uni maths yet or engine maths for that matter...
the sad thing is that i'm going to study computing @ nus this august...i'm going to miss doing and learning maths
-
answer is 3.596?
-
Haha.. no answer de... is the formula to be derived...Originally posted by R3SsH|n:answer is 3.596?
becoz sin^2(x) = 1/2 - 1/2cos(2*x)
The result here is sin^3....
But, how to derived the formula from sin^2??
Haha.. thx again... -
wah liaoz want to torture me with DFT arh?
today just grad lazy to think next day when i free and good mood bah -
Haha.. haven't until DFT yet... only Fourier series nia...Originally posted by hisoka:wah liaoz want to torture me with DFT arh?
today just grad lazy to think next day when i free and good mood bah
No calculas, summation or integration to do yet..
Will need a DFT time scaling or time shifting soon... after this one is solved...
Arigato... -
The first few modules are (almost) maths modules.Originally posted by anonymous_coward:haiz...sorry i can't help you as i've not learn uni maths yet or engine maths for that matter...
the sad thing is that i'm going to study computing @ nus this august...i'm going to miss doing and learning maths