Questions tagged [elementary-functions]
For questions on elementary functions, functions of one variable built from a finite number of polynomials, exponentials and logarithms through composition and combinations using the four elementary operations $(+, –, ×, ÷)$.
630 questions
1 vote
0 answers
52 views
Is there a general criterion for when a function has an elementary inverse? [duplicate]
For some functions (like $f(x)=x+e^x$), we know an inverse exists by monotonicity, but that inverse is not expressible in elementary terms. Is there a general mathematical framework or theorem (beyond ...
0 votes
1 answer
53 views
Constant field is preserved in elementary differential extension?
I'm studying symbolic integration. Liouville's theorem (the version I've learned) states that for an elementary function $f$, if $f'=g$ for some $g$ lying in some elementary differential extension $E=...
6 votes
0 answers
141 views
Adding equality $\frac{1}{2} \left(e^{2 i \pi B_- x}+e^{2 i \pi B_+ x}\right)=x \ln \left(\frac{B_+-x}{B_-+x}\right)$ to umbral calculus
As I understand it, umbral calculus by default only postulates the effect of evaluation operator on umbral expressions. This means, we are free to add more axioms and relations between umbral elements ...
4 votes
1 answer
154 views
Can superposition alone generate the Kalmár elementary function $x^y$ from $⟨x + y, x \bmod y, 2^x⟩$?
In Mihai Prunescu, Lorenzo Sauras-Altuzarra, and Joseph M. Shunia (2025), A Minimal Substitution Basis for the Kalmar Elementary Functions, the authors define a minimal generating set for the Kalmár ...
1 vote
1 answer
89 views
Do we need to include logarithm and exponent directly in the definition of elementary functions if we go from finite to countable function arithmetic?
Inspired by this question. The definition of elementary functions includes finite addition, subtraction, multiplication, division and composition of algebraic functions, trigonometric functions and ...
6 votes
1 answer
276 views
Is the condition about composition needed to stay with the elementary functions?
We use the definition of elementary functions given in Spivak's calculus (with some changes so this is not exactly the same). An elementary function is one which can be obtained by a finite number of ...
2 votes
1 answer
142 views
If the antiderivative of an elementary function is also elementary, can we always compute its indefinite integral with "routine methods"?
"Routine methods" here mean "methods like integration by parts and integration by substitution" (as the original asker referred to) (too long for the title). The original question ...
9 votes
1 answer
289 views
For $x \in \left(0, \frac{\pi}{2}\right]$, prove that $\frac{\sin^4 x}{x^4} + \frac{\sin x}{13} \geq \cos x$.
Let $x \in (0, \pi/2]$. I am trying to prove the following inequality: $$ \frac{\sin^4 x}{x^4} + \frac{\sin x}{13} \ge \cos x. $$ I tried to tackle this by considering known approximations and bounds ...
0 votes
0 answers
93 views
Interpolating polynomial with simple roots
Let $n,m$ be integers with $n > m$. Consider the set of monic polynomials $P(x)$ over $\mathbb{C}$ of degree at most $n$ satisfying the linear constraints on coefficients $$P(x_i) = y_i$$ for some $...
1 vote
1 answer
100 views
The sum of two decreasing functions is always decreasing - Please check my proof. [closed]
would anybody be so kind to check my proof? It is done by contradiction. Any adjustements insights welcomed. Problem: Prove that the sum of two decreasing functions is decreasing. Proof: Suppose $f$ ...
0 votes
0 answers
48 views
chebyschev theorem on the integration of binomial differentials [duplicate]
A binomial differential is definied as $x^m(a+bx^n)^p$ with $a,b\in\mathbb{R}\setminus\{0\}$ and $m,n,p\in\mathbb{Q}$. A Chebichev's theorem (see https://encyclopediaofmath.org/wiki/...
-2 votes
1 answer
117 views
Composite functions [closed]
I have two functions, $f(x)$ and $g(x)$. $f(x) = ax^2$, where $-1 \le x \le 4$. $g(x)$ is a piecewise function: $x+b$ where $-1 \le x \le 0$, and $c-x$ where $0 \le x \le 1$. The two functions have ...
1 vote
0 answers
67 views
Does there exist an elementary number which is not a period?
Periods as defined by Kontsevich and Zagier are complex numbers α whose real and imaginary parts are values of absolutely convergent integrals of rational functions with rational coefficients, over ...
1 vote
0 answers
76 views
Strange technique in integrating [duplicate]
I stumbled across a bland question on integrating $\sqrt{x^2+4}$ and I throw it into the integral calculator, https://www.integral-calculator.com/ Normally this can be solved via hyperbolic/trig ...
0 votes
0 answers
42 views
Elementary function with unbounded derivative near zero and different one-sided limits at zero
I would like to find an elementary function, $f$, with the following properties: $f$ is continuous on [-1,1] except at zero $f'$ is unbounded near zero $\lim_{x\to 0^{+}} f(x)$ and $\lim_{x\to 0^{-}} ...