Dabour Hub EGEgyptian Curriculum 2026/2027
2-1 (a) Polar coordinates and the Argand plane

2-1 (a) Polar coordinates and the Argand plane

Point 1 of 8 — Lesson 1: Complex Numbers in Trigonometric and Exponential Form and De Moivres TheoremQuestion bank: 6 questions (1 with pictures)

01 2-1 (a) Polar coordinates and the Argand plane

Polar and Cartesian coordinates

  • A point A(x,y) at distance r from the origin, with the radius making angle θ with the positive x-axis, has polar coordinates (r,θ).
  • Polar axis: the positive part of the x-axis, from which the angle θ is measured.
  • Polar to Cartesian: x=rcos⁡θ,y=rsin⁡θ
  • Cartesian to polar: r=x2+y2,tan⁡θ=yx
  • So the Cartesian point can be written as (rcos⁡θ, rsin⁡θ).

Argand plane

  • Argand plane (Argand diagram): a Cartesian plane in which the x-axis is the real axis and the y-axis is the imaginary axis.
  • The complex number z=x+yi is represented by the point (x,y) (or by the vector from the origin to that point).
  • Jean-Robert Argand was the first to study complex numbers in detail; he used them to show that every algebraic equation has roots, real or imaginary.

Symmetry on the Argand plane

  • The points representing z and −z are symmetric about the origin.
  • The points representing z and its conjugate zˉ are symmetric about the real axis (x-axis).
  • The point representing z1+z2 is the fourth vertex of the parallelogram built on the vectors of z1 and z2.
  • Example: z1=2+i and z2=−2−i are symmetric about O; z1=2+i and zˉ1=2−i are symmetric about the real axis.

📝 Question bank for this point

6 questions linked to this point only, 1 of them with pictures.