# Answer to Question #45204 in Other Engineering for Golden

Question #45204

1) Show that cos A * cos B = 0.5 [cos(A+B) + cos(A-B)] . Some English is essential in

addition to the algebra. Note that cosine is an even function so that cos(A-B) = cos(BA).

2) A mixer has a local oscillator at 1157 kHz and a bandpass filter centred at 455 kHz.

What are the centre frequencies of signals which would cause output from the filter?

How is it that a radio receiver accepts only one channel of input signal?

addition to the algebra. Note that cosine is an even function so that cos(A-B) = cos(BA).

2) A mixer has a local oscillator at 1157 kHz and a bandpass filter centred at 455 kHz.

What are the centre frequencies of signals which would cause output from the filter?

How is it that a radio receiver accepts only one channel of input signal?

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