(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I make the product [tex]\cos(x)\cos(5x)[/tex] a sum of two cosines. I think this is called linearizing but please correct me if I'm wrong.

(I need it to find the n-th derivative of that function).

2. Relevant equations

3. The attempt at a solution

I know the answer is:

[tex]\frac{\cos(4x)+\cos(6x)}{2}[/tex]

- Thanks HP 50g ;) -

But how do I get to this result?

I think I should be using Moivre's formula but I get both sines and cosines in my formula.

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# Homework Help: Linearizing a cosine

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