Hi,
[Note: The original OP post was a question about how to calculate the frequency of notes in between semi tones]
According to Wikipedia, one cent is the ratio between the two frequencies that is equal to 2^(1/1200).
Thus, if A=440Hz then A plus one cent will be:
440*(2^(1/1200)) Hertz
A plus two cents will be:
440*(2^(1/1200))^2 Hertz
A plus three cents will be:
440*(2^(1/1200))^3 Hertz
A plus N cents will be:
440*(2^(1/1200))^N Hertz
A note with frequency F plus N cents will be:
Fnew=F*(2^(1/1200))^N Hertz
Also,
Fnew/F=(2^(1/1200))^N
or
Fnew/F=2^(N/1200)
or
log(Fnew/F)=log(2)*N/1200
or
1200*log(Fnew/F)/log(2)=N
So if you know Fnew and F and Fnew>F you can find N and you might have to round the answer.
If however Fnew<F then use:
N=1200*log(F/Fnew)/log(2)
or use the first formula and interpret a negative N as 'down' in cents.