# Fourier cosine series

## Homework Equations

All I know is the a's have something to do with the integrals.

## The Attempt at a Solution

I used FFT analysis in Matlab but I do not know what I am looking for. How do the a0s relate to the f(t) in the question and how would I even do run that equation in an excell program. I just need to know where to start.

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kuruman
Homework Helper
Gold Member
I don't think you need FFT analysis for this. Read the problem statement and do what it says using a spreadsheet. It's a simple plug and chug and plot question.

scottdave
Homework Helper
To find the a0, a1, etc. Compare the format of the given summation to the expansion of f(t) in equation (5.2)

To find the a0, a1, etc. Compare the format of the given summation to the expansion of f(t) in equation (5.2)
so would a0 be .2 and a1=(2/pi)(-1)^1/1

I don't think you need FFT analysis for this. Read the problem statement and do what it says using a spreadsheet. It's a simple plug and chug and plot question.
what am I pluging into, how do the a's relate to the f(t).

kuruman
Homework Helper
Gold Member
what am I pluging into, how do the a's relate to the f(t).
You are plugging into the equation ##f(t)=0.2+\frac{2}{\pi} \sum_{n=1}^\infty~...~etc## that is given to you. The posts by @scottdave and @Carter explain what the ##a_n## are, they are whatever multiplies each ##\cos(4n \pi t)## term in the summation.

scottdave