Autocorrelation can recover hidden frequencies and amplitudes from a mixed signal.

Evidence

Suppose you were just given the sum of 10 sinusoidal terms, but you are not told the frequencies or the coefficients. The power of the CAT theorem is that it can pick out the correct frequencies and amplitudes in the sum by comparison with known cosines. — Eric J. Heller, Why You Hear What You Hear- An…, 404

Categorization

• DEFINE: Explains what the Cosine Addition Theorem (CAT) accomplishes operationally.
• XREF: Connects to how a cochlea or Fourier analyzer decomposes a complex waveform into frequency components.