How to find theta_k in terms of theta_i and theta_j in the following formula

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Hayam Wahdan 2019-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/497674-how-to-find-theta_k-in-terms-of-theta_i-and-theta_j-in-the-following-formula

评论： Walter Roberson 2019-12-22

 Theta_k *sqrt(1+theta_k^2) + arcsinh(theta_k) = {theta_j* sqrt(1+theta_j^2)+arcsinh(theta_j)}+{theta_i * sqrt(1+theta_i^2)+arcsinh(theta_i)}

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Answer 1

Walter Roberson 2019-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/497674-how-to-find-theta_k-in-terms-of-theta_i-and-theta_j-in-the-following-formula#answer_407335

在 MATLAB Online 中打开

 F = @(theta_k) (theta_k .* sqrt(1+theta_k.^2) + asinh(theta_k)) - ( (theta_j .* sqrt(1+theta_j.^2) + asinh(theta_j)) + (theta_i .* sqrt(1+theta_i.^2) + asinh(theta_i)));
 
 guess = rand();
 
 fsolve(F, guess)

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Hayam Wahdan 2019-12-22

thank you very much,

but when running these lines of code this error appear " Failure in initial objective function evaluation. FSOLVE cannot continue"

Walter Roberson 2019-12-22

What are the initial values for theta_i and theta_j ?

Perhaps you did not define theta_i and theta_j before you defined F.

If you are trying to find a symbolic form for theta_k in terms of unresolved variables theta_i and theta_k then you are not going to be able to do that, at least not in a closed form.

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