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(cosθ + i sinθ)ⁿ: raising to the power n multiplies the angle by n
θ=40° z¹ = (cos40°, sin40°) z² = (cos80°, sin80°) z³ = (cos120°, sin120°) (cosθ + i sinθ)ⁿ = cos(nθ) + i sin(nθ)

Starting at angle θ=40° on the unit circle. Squaring doubles the angle to 80° (green). Cubing triples it to 120° (red). The point just rotates: its distance from the origin stays 1.

p_04
nth roots of unity: solutions to zⁿ = 1
1 e^(iτ/6) -1 e^(-iτ/6) z⁶ = 1

The 6th roots of unity form a regular hexagon on the unit circle. The nth roots of z^n = 1 always form a regular n-gon, equally spaced at angles 2πk/n = τk/n.

p_06links
Complex multiplication = rotate + scale: angles add, moduli multiply
z₁ θ₁=30° z₂ θ₂=50° z₁·z₂ θ₁+θ₂=80° |z₁|·|z₂| = moduli multiply. arg(z₁·z₂) = θ₁ + θ₂ De Moivre: (e^iθ)ⁿ = e^(inθ) multiplying n times adds angle n times

When you multiply two complex numbers, their angles (arguments) add and their magnitudes multiply. If both numbers sit on the unit circle (magnitude 1), only the angles change. Multiplying n times adds the angle n times: that is De Moivre's theorem.

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