Linked Questions

3
votes
2answers
261 views

Eigen values of a third order linear homogenous ODE

From a system of PDEs where i used the following ansatz: $$\theta_w(x,y) = e^{-\beta_h x} f(x) e^{-\beta_c y} g(y)$$. $F(x) := \int f(x) \, \mathrm{d}x$ and $G(y) := \int g(y) \, \mathrm{d}y$ So, $$\...
4
votes
2answers
148 views

eigenvalue and eigenfunction of complex euler-bernoulli beam

So I am new to Mathematica and am trying to solve the euler-bernoulli modal equation for a U-shaped Cantilever beam given by equations :- where i is the index of the region. In total there are 2 ...
27
votes
4answers
9k views

How to find numerically all roots of a function in a given range?

It is common that I search numerically for all zeros (roots) of a function in a given range. I have written two simple minded functions that perform this task, and I know of similar functions on this ...
1
vote
1answer
70 views

RootSearch warning “too small to represent as a normalized machine number”

RootSearch is a package for finding all roots within a range from Ted Ersek. As I test it, it is quite robust. But I also encountered some issue that I can not resolve. I define a function ...
0
votes
0answers
56 views

Using Reduce with a Interpolation function

I am trying to find all the solutions of an equation that contains an interpolation function int, where int=Interpolation[data] (...
0
votes
0answers
43 views

How can we deal with initial value sensitivity of FindRoot?

Recently, I have tried to find minima of some functions with FindMinimum, but those are so flat that the results cannnot be reliable. So I switched the method to ...
2
votes
4answers
92 views

Selecting data from a list

Let's create a simple data list Clear["Global`*"]; data = Table[{i, Sin[i]}, {i, 0, 6 \[Pi], 0.01}]; L0 = ListPlot[data] Now I want to find for which values of $...
9
votes
5answers
531 views

NDEigenvalues vs. FindRoot for finding the eigenvalues of Airy equation?

Say I am trying to find the first 5 eigenvalues of the differential equation $f''(x)=\lambda x f(x)$, on the interval [-1,0], with boundary conditions $f(-1)=f(0)=0$. I will try to do this 3 ways, ...
1
vote
2answers
94 views

Finding positive region of continous function

I want to find (and plot) the positive region (within a certain domain say x<3,y<3) of a function ...
13
votes
6answers
831 views

Solving this challenging ODE

Consider the ODE: $$w^{(4)}(x) + (L-x)w''(x) - w'(x) = 0 $$ with some of the following boundary conditions: free: $w'' = 0$, $w'''=0$, clamped: $w = 0$, $w'=0$, pivot: $w = 0$, $w''=0$. Two such ...
1
vote
0answers
56 views

How to find x for certain y from InterpolatingFunction [duplicate]

As shown in the picture, I get the data after using NDSolve. Now I want to get the x for cetain y, how can I do this? The last three lines is the way I try to ...
75
votes
5answers
25k views

How to find all the local minima/maxima in a range

I want to find : all local maxima in range all local minima in range From those points I can interpolate and combine functions upper and lower boundary. What I am really interested in, is the mean ...
5
votes
3answers
700 views

How can I solve this equation: $(47^{(u + 1)} + 3^{(u + 1)})/(u + 1) ==50^{1.5}/1.5$?

Solve[(47^(u + 1) + 3^(u + 1))/(u + 1) ==(50^1.5)/1.5,u] The code I tried is above, but it showed me a message problem "Solve was unable to solve the system ...
5
votes
3answers
802 views

Why does the following Solve take so long?

Why does the following take Mathematica so long to reply to? Solve[BetaRegularized[0.5, k, n - k - 1] == 0.035, k] where $n = 1000$ By the way, In case there is ...
2
votes
1answer
184 views

Complex roots of the determinant of symbolic matrix

I am trying to find multiple complex and real roots of the determinant of symbolic matrix. Someone advised me to use Muller's method. I am wondering if there is a package already written to do this ...

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