Before revision: However, when the input is a sinusoid of the form , using product-to-sum trigonometric identities it can be easily shown that the output is , that is, the output doesn't consist of just one sinusoid of same frequency as the input (), but instead also sinusoids of frequency and .
After revision: However, when the input is a sinusoid of the form , using product-to-sum trigonometric identities it can be easily shown that the output is , that is, the output doesn't consist of just one sinusoid of same frequency as the input (), but instead also of sinusoids of frequencies and s; furthermore, the fundamental frequency of the input is , which is different than that of the inputonly of sinusoids .