The problem asks me to show that the addition of two cosines with different wavelength and frequencies gives a solution with beats.(adsbygoogle = window.adsbygoogle || []).push({});

Mathematically, I need to verify that A cos (k1x-w1t)+A cos (k2x-w2t) is equivalent to A cos (.5(k1+k2)x-.5(w1+w2)t) cos (.5(k1-k2)x-.5(w1-w2)t)

I converted the second equation into exponential form (cos (kx-wt)=1/2(e^i(kx-wt)+e^-i(kx-wt)), multiplied the resulting binomials together, and simplified to get the first equation. My problem is with the constant, A. How do I deal with it? I need A/2 for the first equation, but simplication of the second yields A/4. How to resolve this?

Any help greatly appreciated!!

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# Homework Help: Wave mechanics?

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