Alternative way to prove that the sum of the square reciprocals is ${\pi^2}/6$
2302
Different methods to compute $\sum\limits_{k=1}^\infty \frac{1}{k^2}$ (Basel problem)
13291
Proving $\sum_{k=1}^n\frac1{\sqrt k}<2\sqrt n$ by induction
130078
How can one prove that $\pi^4 + \pi^5 < e^6$?
10675
Proving that $\frac{1}{2\pi}\int_{0}^{2\pi}|f(re^{it})|^2dt=\sum_{n=0}^{\infty}|a_n|^2r^{2n}$
150310
A finite sum of reciprocals of complex numbers cannot be confined to a half-plane
146512
Prove that for every prime number $p>3$, $4p^2+1$ can be written as the sum of three square numbers
140841
Induction proof of lower bound for $\sum \sqrt n$
67502
Sum of reciprocal prime numbers
67605
Different proof that $\sqrt{2}$ is irrational
29886
How to evaluate $\int_0^1\int_0^1 \frac{1}{1-xy} \, dy \, dx$ to prove $\sum_{n=1}^{\infty} \frac{1}{n^2}=\frac{\pi^2}{6}$.
138267
What is the sum of Fibonacci reciprocals?
24222
Sum of the squares of the reciprocals of the fixed points of the tangent function
63474
Showing $\sum_{i = 1}^n\frac1{i(i+1)} = 1-\frac1{n+1}$ without induction?
87242
Ways to prove $ \int_0^\pi dx \frac{\sin^2(n x)}{\sin^2 x} = n\pi$
143113
Non-inductive, not combinatorial proof of $\sum_{i \mathop = 0}^n \binom n i^2 = \binom {2 n} n$
130027
Give a direct proof of the fact that $a^2-5a+6$ is even for any $a \in \mathbb Z$
134885
proving that $\mathbb{Q}(\sqrt{5}, \sqrt{6}) = \mathbb{Q}(\sqrt{5}+ \sqrt{6}) $