# Topics

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Aegyptian (fractions) p/q=1/a+1/b+1/c...
Amicable (numbers) Each one is the sum of divisors of the other
Antiparallel Antiparallel lines
Arithmetic (sequence) Un+1=Un+a
Bernoulli (numbers) 1, -1/2, 1/6, 0, -1/30, 0, 1/42...
Bezier (curves) interpolate with Bezier curves
Bézout (theorem) GCD(a,b)=1 <=>au+bv=1
Bretschneider Heron, Bretschneider and Brahmagupta relations
Brianchon (theorem) Pascal and Brianchon theorems
Butterfly (theorem) Butterfly theorem
Cayley-Menger (determinant) Volume of a tetrahedron, Piero della Francesca formula
Ceva (theorem) Concurrent lines
Congruence Remainders and modulo...
Congruent (numbers) x²±n=y²
Conic sections Ellipses, hyperbolas et parabolas
Descartes (formulae) relation of touching circles radii
Diophantine (equations) ax + by = c
Divisors Number and sum of divisors of n
Equation (2nd degree) ax²+bx+c=0
Equation (3rd degree) ax³+bx²+cx+d=0
Equation (4th degree) ax4+bx³+cx²+dx+e=0
Euclide (algorithm) Calculation of GCD
Euler (cycle) Going through all lines of a graph
Euler (line) Euler line and Euler circle
Euler (relation) Relation between radius od incircle and circumcircle
Euler (formulae) Relation S+F=A+2 in a polyhedron
Fermat (numbers) Prime numbers 2n+1
Feuerbach (theorem) Euler circle touches incircle and excircles
Fibonnaci (numbers) 1,2,3,5,8,13...
Fractals Koch curve, dragons, Mandelbrot set...
Geometric (sequence) Sum of a geometric series
Grinberg (relation) necessary condition for hamiltonian circuit
Hammiltonian (path) Going through all vertices of a graph
Harmonic (conjugate) Relative to 2 lines, a circle or a conic section
Heron Heron, Bretschneider and Brahmagupta relations
Incircle Some property of incircle and excircles
Inversion Circle inversion
La Hire (theorem) Draw ellipses
Lemoine (point) Intersection point of symedians
Mascheroni Constructions with compass alone
Mersenne (numbers) Prime numbers 2n-1
Napoleon (Problem) Some Napoleon problems
Pascal (theorem) Pascal and Brianchon theorems
Pell (equation) x²-Dy²=K
Perfect (Numbers) Number equals the sum of its divisors
Planar (graph) Drawn on a plane without crossing edges
Pole and polar Relative to 2 lines, a circle or a conic section
Powers (sum of) 1+2n+3n+4n...
Projective (geometry) Basic notions in projective geometry
Ptolemy (theorem) xy = ac+bd
Pythagora (theorem) x²+y²=z²
Pythagora (triples) x²+y²=z²
Renaldini Approximate constructions of regular n-gon
Soddy (formulae) relation of touching circles radii
Soddy (point) Circles touching three others, isoperimeter point
Squares (sum of) n=x²+y²+...
Squaring (the circle) Approximate constructions
Triangular (numbers) 1,3,6,11...
Trigonometric (relations) About cos(a+b) etc...
Trigonometric (values) Specific values of sin(x) etc...