Path: news.mathworks.com!not-for-mail From: "John D'Errico" <woodchips@rochester.rr.com> Newsgroups: comp.soft-sys.matlab Subject: Re: how to solve trigonometric equation Date: Wed, 8 Jun 2011 02:20:06 +0000 (UTC) Organization: John D'Errico (1-3LEW5R) Lines: 28 Message-ID: <ismm8l$3bt$1@newscl01ah.mathworks.com> References: <ismjm4$qe6$1@newscl01ah.mathworks.com> Reply-To: "John D'Errico" <woodchips@rochester.rr.com> NNTP-Posting-Host: www-01-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: newscl01ah.mathworks.com 1307499606 3453 172.30.248.46 (8 Jun 2011 02:20:06 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Wed, 8 Jun 2011 02:20:06 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 869215 Xref: news.mathworks.com comp.soft-sys.matlab:730735 "Philippe " <philippeb3@hotmail.com> wrote in message <ismjm4$qe6$1@newscl01ah.mathworks.com>... > Dear all, > > I would like to solve the following equation between 0 and 2 pi. > > A*sin(w*t-p)+2*B*sin(2*w*t-q)=0 > > where A, B, w, p, q are constants. > > t=? > > Is there any way in Matlab to solve this equation? You can do it by hand. Start with the sin of a sum identity to get rid of those p and q terms. sin(x+y) = ... Then reduce sin(2*x) using a similar identity. In the end, you reduce this to a polynomial in sin(w*t). Solve for the roots of that polynomial. Once you know all possible solutions, then compute t using an asin. You do the work though, not me. John