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I am having a problem solving the following equation. Please help.

$12(\cos(x))^3+2\cos(x)^2+(24\sin(x)-3)\cos(x)+2\sin(x)= 0$

Thank you in advance

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What does this have to do with calculus? Also, what have you tried already? –  anorton Oct 29 '12 at 18:25
    
Well I don't really know where to start.. –  user43418 Oct 29 '12 at 18:25
    
Have you tried factoring by grouping? –  Ben Oct 29 '12 at 18:26
    
What does that mean ? –  user43418 Oct 29 '12 at 18:27
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So apparently, it isn't possible to determine exact values of x... –  user43418 Oct 29 '12 at 18:56

1 Answer 1

up vote 2 down vote accepted

$s = \sin(x)$ must satisfy the equation $144\,{s}^{6}-576\,{s}^{5}+220\,{s}^{4}+1000\,{s}^{3}-283\,{s}^{2}-424 \,s-77 = 0$. This has Galois group $S_6$, so it can't be solved in terms of radicals. Thus you aren't going to get nice closed-form solutions. The four solutions for $0 \le x \le 2 \pi$ are approximately $1.66661701719437, 3.42548142597468, 4.63849563287631, 5.91793801389173$ (found by numerical methods).

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Do you mean that I can't find exact solutions? –  user43418 Oct 29 '12 at 18:48
1  
That's right, you can't. –  Robert Israel Oct 29 '12 at 19:52

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