Vol. 4 · Numbers that rotate

Complex Numbers and Vectors

A companion to 《复数与向量》 by Zhang Sihui · 9 stops ·

Vol. 1Vol. 2Vol. 3Vol. 4Vol. 5Vol. 6Vol. 7Vol. 8

  1. Ch. 1Complex Numbers and Their AlgebraAdd one new number with i² = −1: complex numbers are points of the plane.ConceptM10M12
  2. Ch. 2Modulus and Argument (I)In polar form, multiplying means: moduli multiply, arguments add.ConceptM11
  3. Ch. 3Complex Numbers and Equations|z−a| is a distance: modulus equations are curves; non-real roots pair up.ConceptM1
  4. Ch. 4Adding and Subtracting VectorsVectors slide freely: chain them head to tail to add; a closed chain sums to 0.Concept
  5. Ch. 5The Inner Producta·b is the length of a times the signed shadow of b on a.ConceptM8
  6. Ch. 6Vectors in SpaceWith coordinates, angles and distances in a solid become arithmetic.Concept
  7. Ch. 7Roots of Unity and Their UsesRoots of unity form a regular n-gon and sum to 0, which filters coefficients.ConceptM9M15
  8. Ch. 8Modulus and Argument (II)Bound moduli with the triangle inequality; herd arguments into a half-plane.Method
  9. Ch. 9Applications of Complex Numbers and VectorsPoints as complex numbers: rotations are products, concyclic means a real ratio.Method