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Topic: 3 equation of cosine law
Replies: 8   Last Post: Apr 2, 2013 6:34 PM

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Torsten

Posts: 1,477
Registered: 11/8/10
Re: 3 equation of cosine law
Posted: Mar 28, 2013 3:44 AM
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"DHAAH JOHARI" wrote in message <kiveni$nan$1@newscl01ah.mathworks.com>...
> "Torsten" wrote in message <kip1uf$5ot$1@newscl01ah.mathworks.com>...
> > "DHAAH JOHARI" wrote in message <kik48r$k5a$1@newscl01ah.mathworks.com>...
> > > > I think you want to use "cosd" instead of "cos" in your equations.
> > > >
> > > > Best wishes
> > > > Torsten.

> > >
> > > Thanks Torsten..thank you very much!
> > > but I still didn't get the answers,..
> > > It said error..i don't know how to fix it
> > >
> > > syms xyz
> > > solutions = solve('x^2 = y^2+233600-966.64*y*cosd(z-65.56) ',' x^2 = y^2+155600-788.92*y*cosd(z-59.53)','x^2 = y^2+97600-624.82*y*cosd(z-50.19)')
> > > [solutions.x solutions.y solutions.z]

> >
> > I think cosd does not accept symbolic arguments.
> > Convert 65.56°, 59.53° and 50.19° to radians and try again.
> > And define
> > syms x y z
> > instead of
> > syms xyz
> >
> > Best wishes
> > Torsten.

>
> Thanks again Torsten..
> i have converting the 65.56°, 59.53° and 50.19° to radians and define syms x y z..but i still didn't get the answers..
> is it right if i wrote like this..so sorry to have bothered you
>
> syms x y z
> solutions = solve('x^2 = y^2+233600-966.64*y*cos(z-1.14) ',' x^2 = y^2+155600-788.92*y*cos(z-1.04)','x^2 = y^2+97600-624.82*y*cos(z-0.88)')
> [solutions.x solutions.y solutions.z]


What do you get if you execute
syms x y z
solutions = solve(x^2 == y^2+233600-966.64*y*cos(z-1.14), x^2 == y^2+155600-788.92*y*cos(z-1.04), x^2 == y^2+97600-624.82*y*cos(z-0.88))
[solutions.x solutions.y solutions.z]
and why is this solution not the solution you expect ?

If I insert
x=444.46, y=149.25
into the equation and solve each equation seperately for z, I _don't_ get the same z-values (for the first equation, I get z=2.29, for the second 2.78 and for the third z=3.44)
So I don't understand why you think that
x=444.46, y=149.25
is a solution.

Best wishes
Torsten.



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