# Numerical solution to a larger equation.

조회 수: 1 (최근 30일)
Prasenjit Dewanjee 2023년 4월 4일
댓글: Dyuman Joshi 2023년 4월 5일
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.
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Dyuman Joshi 2023년 4월 5일
"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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### 답변 (1개)

Torsten 2023년 4월 5일
편집: Torsten 2023년 4월 5일
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
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Alex Sha 2023년 4월 5일
There are infinite solutions (including 0)：Lamda2 = n*pi，where n=[...,-5,-4,-3,-2,-1,0,1,2,3,4,5,...]
Torsten 2023년 4월 5일
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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