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Topic: Using Solve/FSolve for Multiple Trig Equations
Replies: 7   Last Post: May 4, 2013 8:44 AM

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Nasser Abbasi

Posts: 5,653
Registered: 2/7/05
Re: Using Solve/FSolve for Multiple Trig Equations
Posted: May 1, 2013 2:24 PM
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On 5/1/2013 11:16 AM, Jung wrote:
> Hello,
>
> I am trying to solve for:
> y
> r
> p
>
> in the following equations where I, J, K are known.
>
> I = siny * sinr + cosy * sinp * cosr
> J = -siny * cosr + cosy * sinp * sinr
> K = cosy * cosp
>
> The code I have used is:
>
> syms r p y i j k
>
> S = solve(i == sin(y)*sin(r)+cos(y)*sin(p)*cos(r), j == -sin(y)*cos(r)+cos(y)*sin(p)*sin(r), k == cos(y)*cos(p))
> S.r
> S.p
> S.y
>
> but I cannot seem to get a result.
>



it is normally very hard to obtain analytical solutions for
trig equations since these are nonlinear and involves inverse functions
with branch cuts as well. So to solve for 'y','p', and 'r'
about, you might want to try a numerical approach.

But I am not an expert in this.

--Nasser




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