What are the principal frequencies that appear at the output of a mixer circuit?

When two signals at frequencies f1 and f2 are applied to a non-linear mixer, the output contains a complex blend of signals. The most prominent, or principal, frequencies present at the output are the original input frequencies (f1 and f2) and their first-order intermodulation products: the sum (f1 + f2) and the difference (f1 - f2). Distractors mentioning square roots or specific multipliers like 1.414 (which relates to RMS voltage, not frequency calculation) are mathematically incorrect for frequency mixing. While harmonics (multiples of the input frequencies) are generated, the core operation of a mixer relies on producing the sum and difference frequencies alongside the originals.