So what I did was Laplace transform $f(t)$ to $F(s)$ and then plug in $s=jw$. However, when I tried this for $cos(3t)$, $$F(jw)={jw\over9-w^2}$$ was the answer. I don't know if this is correct, and I'm not satisfied since I would intuitively expect dirac functions at w=3 and -3. Could anyone clarify what I did wrong? Thanks.
2026-04-03 17:26:18.1775237178
Fourier transform from Laplace transform
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