# Questions tagged [assumptions]

• 179
50 views

### Assisting Solve to generate solution to a complicated equation

I have the following Mathematica code: ...
• 2,263
1 vote
110 views

### FunctionPoles with arbitrary undefined function

Good day everyone. I have very simple question about behaviour of the functions FunctionPoles, FunctionMeromorphic e.t.c. Can these functions work properly with undefined functions? For example when I ...
• 69
104 views

### Assume asymptotic value in a limit?

Is it possible to give Mathematica a limit about's function at infinity? For example I would like to ...
• 770
54 views

### Subtituting kronecker deltas for products in simplification

I have a problem where I have some vector, $a = (a_1, a_2, \ldots, a_n)^T$ that I want to have a Kronecker delta multiplication rule, $a[i]a[j] = \delta_{ij}$ (these are basically basis vectors, but ...
1 vote
30 views

### Making an "unsafe" simplify that ignores the validity conditions of simplifications

Mathematica will never make assumptions you don't tell it to make, and will state all conditions under which the answers it gives are valid. While this is overall a good thing, this often leads to ...
• 111
62 views

### Refine not able to simplify for PositiveReals

If I type in Mathematica Refine[d^2 == a^2, {a ∈ PositiveReals, d ∈ PositiveReals}] I get d^2 == a^2 Why don't I get ...
110 views

### How to tell Mathematica to solve an equation assuming all solutions are non-negative reals? [closed]

The title. I have a system of 6 equations that I want to solve. The system is non-linear. I want to solve it, but I just want Mathematica to give me solutions that are non-negative reals (so no ...
1 vote
185 views

### How can I force Mathematica to calculate this integral?

I have the following expression. I realize Mathematica has a little bit of trouble with Abs[] as it assumes variables to be complex and etc., but I am trying to compute an integral and it just keeps ...
1 vote
69 views

### Finding the (symbolic) eigenvalues of a matrix with some assumption

I have the following 3$\times$3 symmetric matrix with symbolic entries. Meff = \begin{array}{ccc} 2 \beta \text{c12}^2 \text{c13}^2 \text{$\eta$11} \text{m1}+\alpha \text{c13}^2 \text{D31} \text{...
1 vote
46 views

### Enforcing the continuity of solutions throughout the whole range of variable in NDSolve, when there are multiple solutions

I am solving differential equations numerically by using NDSolve. Let's say that the function that I want to obtain is f[t]. Then, it turns out that my differential equation is a sextic polynomial of ...
89 views

### Why do I get different results for this complex line integral?

I want to compute line integral of $f(z) = \frac{1}{z(z-1)^{n+1}}$ over a closed curve $\gamma: t \mapsto 1 + \frac{1}{2} e^{i t}, t \in [0,2\pi]$ in the complex plane in two different ways but the ...
• 153
271 views

### How can I make assumptions in NDSolve?

Suppose I try to solve the following differential equation numerically. (My example is much more complicated, but for simplicity, let's consider this example.) ...
1 vote
37 views

### Is there a nice way to deal with sets in an abstract/symbolic way?

For instance, if I wanted to declare $A$ to be the set of all finite subsets of $\mathbb{Z}$, and declare $B$ to be a set comprising all finite subsets of $\mathbb{Z^{-}}$, and then declare $C$ to be ...
• 763
47 views

### Double variable integration unable to prove that integration limits are real

I have simple question regarding double integrating a function. J*Integrate[Integrate[Cos[ArcTan[Sqrt[(x - a)^2 + (y - b)^2]/L]], {b, -b, b}], {a, -a,a}] The error ...
• 23
89 views

### Simplify and Assumptions

Am I missing something here? Thanks for any help! SN
1 vote
36 views

### Limitations of Assumptions

Why don't Simplify[x[2, 1] < x[1, 3], Assumptions -> {x[a_, b_] > x[c_, d_] /; a > b && c < d}] or ...
• 643
64 views

### Integral behaviour?

I'm trying to find a standard integral, which shows itself up in general relativity (proper distance in Schwarzschild metric). For example in this video. The integral is shown as where $r_s< r$ ...
• 770
249 views

### Why does the assuming not work as expected?

Why does this not work? I expect the output would be something like 1/s*e^-(sT). ...
• 593
I have a very long function for $\{x,b\}\in\mathbb{R}$ and $n=\{1,2,3,4,5,6,7,8,9,10\}$; here, I have only mentioned a short part of that. The function is a sum of the complex exponentials (a picture ...