Numerical solution to a larger equation.

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Prasenjit Dewanjee
评论： Dyuman Joshi 2023-4-5
Hi!
I have a very large and complicated equation:
sinh(5.9605e-08*(((1.1259e+15*lamda2^2 + 7.5126e+15)^2)^(1/2) + 7.5126e+15)^(1/2))*sin(2*lamda2)*(lamda2^2 + 8.8818e-16*((1.1259e+15*lamda2^2 + 7.5126e+15)^2)^(1/2) + 6.6725)=0
I need to solve for lamda2. Matlab is unable to solve this. I am getting only 0 as answer. It should not be zero.
Any help will be appreciated.
  1 个评论
Dyuman Joshi
Dyuman Joshi 2023-4-5
"Matlab is unable to solve this."
What makes you think so? How did you try to solve it?
"It should not be zero."
Why not? Zero is a root to the equation.
There are infinite solutions to the equation as mentioned by @Alex Sha below, Which other values do you want as the solution?

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回答（1 个）

Torsten
Torsten 2023-4-5
编辑：Torsten 2023-4-5
Ran in:
What is the zero of your choice ?
fun = @(lamda2)sinh(5.9605e-08*(((1.1259e+15*lamda2^2 + 7.5126e+15)^2)^(1/2) + 7.5126e+15)^(1/2))*sin(2*lamda2)*(lamda2^2 + 8.8818e-16*((1.1259e+15*lamda2^2 + 7.5126e+15)^2)^(1/2) + 6.6725);
lamda2 = -3.2:0.001:3.2;
flamda2 = arrayfun(@(lamda)fun(lamda),lamda2);
plot(lamda2,flamda2)
grid on
  2 个评论
Alex Sha
Alex Sha 2023-4-5
There are infinite solutions (including 0)：Lamda2 = n*pi，where n=[...,-5,-4,-3,-2,-1,0,1,2,3,4,5,...]
Torsten
Torsten 2023-4-5
@Alex Sha
You are correct, I missed the sin(2*lamda2) term. So lamda2 = n/2 * pi (n integer) are roots of the function.

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