Thanks. Am Sonntag, 22. Dezember 2019 16:33:29 UTC+1 schrieb Chris Smith: > > Another approach for these problems is to use, as a starting point, > solutions to a simpler problem which become initial guess to the more > difficult problem. e.g. solving sin(x)=0.2 will give you two solutions and > as many others as you want by adding or subtraction 2pi. Then these > approximate solutions can be used as initial guesses for nsolve as you > change the problem to `sin(x)-(a*x+0.2)` with `a` increasing as quickly as > possible from 0 to 0.5 (in your case). This is the "continuation" method. > > /c > > On Saturday, December 21, 2019 at 2:17:52 AM UTC-6, Philipp Gressly > Freimann wrote: >> >> Hello >> >> Well, thanks a lot. Works great. I did not know the "nsolve" command. >> >> If I am right, there is no command to find all three solutions? >> >> φ >> >> Am Freitag, 20. Dezember 2019 11:48:03 UTC+1 schrieb Oscar: >>> >>> You can use nsolve to find numerical solutions: >>> ``` >>> In [10]: nsolve(Eq(sin(x), 0.5*x + 0.2), x, 0) >>> Out[10]: 0.425436108484597 >>> ``` >>> This will find one root at a time starting from an initial guess (I've >>> used zero). >>> >>> Initial guesses -1 and +1 give two other roots. >>> ``` >>> In [11]: nsolve(Eq(sin(x), 0.5*x + 0.2), x, -1) >>> Out[11]: -2.11307244875263 >>> >>> In [12]: nsolve(Eq(sin(x), 0.5*x + 0.2), x, +1) >>> Out[12]: 1.59919364642736 >>> ``` >>> >>> You can get more precise solutions using prec: >>> ``` >>> In [15]: nsolve(Eq(sin(x), 0.5*x + 0.2), x, 0, prec=50) >>> Out[15]: 0.42543610848459725447179186114511470949330179080539 >>> ``` >>> >>> -- >>> Oscar >>> >>> On Fri, 20 Dec 2019 at 10:26, Philipp Gressly Freimann >>> <[email protected]> wrote: >>> > >>> > Hello >>> > >>> > I want to solve the following equation numerically between -PI and PI: >>> > >>> > sin(x) = 0.5x + 0.2 >>> > >>> > [which is similar to sin(x) - 0.5x - 0.2 = 0] >>> > >>> > The graph shows me three solutions. Is there a possibility to solve >>> this equation numerically using sympy? >>> > >>> > Thanks in advance >>> > >>> > φ >>> > >>> > -- >>> > You received this message because you are subscribed to the Google >>> Groups "sympy" group. >>> > To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> > To view this discussion on the web visit >>> https://groups.google.com/d/msgid/sympy/abc402b1-ac1a-4508-95a8-c13a48483654%40googlegroups.com. >>> >>> >>> >>
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