Proof of one of the most beautiful equations in Math.
2302
Different methods to compute $\sum\limits_{k=1}^\infty \frac{1}{k^2}$ (Basel problem)
48502
number of ordered pairs of integers $(x,y)$ satisfying the equation
26790
Proving the geometric sum formula by induction
157200
Roots of a equation on a complex plane
145759
formal proof from calulus
126445
Proving the second root of a quadratic equation
142318
Mathematical roses with $4n+2$ petals
108885
Systems of equations with a single number
108118
Poincaré-Bendixon show periodic solutions.
67243
Applications for the class equation from group theory
103347
combinatorial proof of summation
92802
Proof of Borsuk-Ulam Theorem .
158063
A formula for the roots of a solvable polynomial
22840
The sum of the first $n$ squares is a square: a system of two Pell-type-equations
141643
Showing $\rho (x,y)=\frac{d(x,y)}{1+d(x,y)}$ is a metric
77253
Proof of Lagrange Identity
31027
Ahlfors "Prove the formula of Gauss"