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From: "Philippe " <philippeb3@hotmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: how to solve trigonometric equation
Date: Wed, 8 Jun 2011 16:35:23 +0000 (UTC)
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> Sure. Just follow my instructions. I told you exactly
> what needed to be done.
> 
> Let Z = sin(w*t).
> 
> A*Z - B*cos(wt) + C*Z*cos(wt) + D*Z^2 - D = 0
> 
> Of course, we can get the cos in terms of the sin.
> 
> cos(w*t) = sqrt(1-Z^2)
> 
> A bit more algebra will rid you of the square roots.
> (Hint isolate the square root term, and square.)
> 
> In the end, you have a 4th degree polynomial in Z.
> 
> Once you have the roots of this poly in Z, can you
> solve for t? (Yes.)
> 
> Just a bit of simple algebra.
> 
> John

Again, following your advice I got

(D+C^2)*Z^4+(2*A*D-2*B*C)*Z^3+(-2*D^2+A^2-C^2+B^2)*Z^2+(-2*B*C)*Z+B^2 = 0

The roots are...no idea...