Numarical solution of an equation with summation

I an trying to solve numericly an equation with two infinite sums of trigonometric functions that equels to a polynomial.

The variable I am trying to get from the equation is in the trigonometric functions and the polynomial.

Can anybody tell me how to approach it?

[Torsten]

Could you state the problem more precisely ?

[Tevel Hedi]

something that looks like that. x is the variable, are the summation coefficients and everything else is a constant.

[Torsten]

And what is given and what is unknown ?

What is the interval on which the approximation should be valid ?

[Tevel Hedi]

i know everything except x who I try to get. And sorry but I dont understand the last question I am new to it.

[Torsten]

And what is a_n and b_n ?

Don't you mean perhaps

sum(an*sin(dn*x))

and

sum(bn*sin(gn*x)) 

instead of

sum(an*sin(d*x))

and

sum(bn*sin(g*x)) 

Otherwise, you could take sin(d*x) and sin(g*x) out of the sum.

[Tevel Hedi]

ye thank you I do mean that! oops

[Torsten]

After your description, this is a root-finding problem in the scalar variable x.

Read the documentation for "fzero" or "fsolve" on how to set up the problem.