Plancherel's Theorem states that for f∈L2(R) we have
f(x)=1√2π∫∞−∞F(k)eikxdk⟺F(k)=1√2π∫∞∞f(x)e−ikxdx.
If we consider f(x):=δ(x) (the delta function) then using this theorem it follows simply that δ(x)=12π∫∞−∞eikxdk.
Clearly then for x=0 and x≠0 the integral is divergent. Also, apparently δ(x) is not square integrable, hence I'm not sure that we can even use Plancherel's Theorem. But having said that I understand that this result does hold. Is it incorrect to show that this result is true using Plancherel's Theorem?
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