prove $f$ is a constant
113343
$f$ is constant if derivative equals zero
96539
is $f$ constant or dilation
23436
$f$ Holder continuous with Holder exponent $p>1\implies f \text{ is constant}$
100765
If $f'(x) = 0$ for all $x \in \mathbb{Q}$, is $f$ constant?
121771
Proof $f(x)\equiv 0$
56967
Show that $ f^2 − g^2 = C $ for some real constant C
151958
How to show $f'(0)$ exist and is equal to $1$?
47474
Proving $|f(z)|$ is constant on the boundary of a domain implies $f$ is a constant function
93400
Prove that an analytic function with a constant imaginary part is constant itself
10727
Let $f$ be an entire function and $L$ a line in $\mathbb{C}$ such that $f(\mathbb{C})\cap L=\emptyset$. Show that $f$ is constant function.
115636
Show that $f$ is either injective or a constant function.
137043
To show that function is constant
112211
Show an increasing function f from omega_1 to R is eventually constant
91352
If $\Re(f)$ is bounded then f is constant.
11158
Proof that a continuous function with $f(x) = f(x^2)$ is constant.
89537
$ \int_0^x f(t)dt=\int_0^{ax}f(t)dt+ \int_0^{bx}f(t)dt$ implies $f$ constant
72856
Show $f$ is constant if $|f(x)-f(y)|\leq (x-y)^2$.