One can look into any precalculus book and find a proof of the addition formulas of sine and cosine. Though as most are aware there is a quick way to get the formulas by using Euler's Formula. But to get the formulas by eulers formula, you must equate coefficients with respect to the imaginary part(adsbygoogle = window.adsbygoogle || []).push({}); i.

My question is this, equating coefficients was taught to be used for polynomials, because a set of coefficients uniquely determines a polynomial. How can you show the same is true with respect toi? Yes it looks very intuitive, but I'm wondering if there's something a little more powerful than that.

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# Euler's Forumla, Trig Addition, and Equating Coefficients

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