I am fairly new to Mathematica, so this may be a simplistic question, but I want to learn. I know how to use the Solve function to solve a single equation like this:


and I know how to use Solve to solve a trigonometric equation like this:


However, when I try to solve my equation using Solve or NSolve Nothing comes up. I use following code


What do I need to do to get Mathematica to give me a value of theta in degrees? I am sure there is a straightforward solution, but I just can't seem to find it. Thank you!


1 Answer 1


If you fix sin to Sin and help NSolve (not Solve) a little by giving range of x then it can do it

equation = Cos[41.614 - x] - 1.2752*Cos[1.607*x] + 7.1644*Sin[1.607*x] == 0; 
NSolve[equation && -4*Pi < x < 4*Pi, x]


{{x -> -11.5371}, {x -> -9.61635}, {x -> -7.76423}, {x -> -5.83644}, \
{x -> -3.81118}, {x -> -1.77431}, {x -> 0.180699}, {x -> 
   2.03885}, {x -> 3.93373}, {x -> 5.93711}, {x -> 7.98094}, {x -> 
   9.96783}, {x -> 11.8458}}

Solve can't solve this type of equation. Need to use numerical solver.

  • $\begingroup$ Thanks a lot. It works now. $\endgroup$
    – Ahlam
    Apr 8, 2020 at 7:43

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