U3 Complex Numbers(KA/PRE/U3)
Unit 3: Complex Numbers
The Complex Plane
Complex numbers are represented as points (or vectors) on a plane where the x-axis is the real part and the y-axis is the imaginary part.
Modulus and Argument
The modulus of a complex number z = a + bi is √(a² + b²). The argument (angle) is the angle with the real axis.
Polar Form of Complex Numbers
z = r (cos θ + i sin θ) = r·e^(iθ)
Graphically Multiplying Complex Numbers
Multiplying complex numbers adds their angles and multiplies their moduli.
Complex Conjugates
The conjugate of z = a + bi is a - bi. It reflects the point across the real axis.
Distance and Midpoint of Complex Numbers
Distance between z₁ and z₂ is √[(a₂ - a₁)² + (b₂ - b₁)²]. Midpoint is ((a₁ + a₂)/2, (b₁ + b₂)/2).
Fundamental Theorem of Algebra
Every non-zero polynomial of degree n has exactly n complex roots (counting multiplicity).
Quiz: Test Your Understanding
What is the conjugate of z = 3 + 4i?
- 3 + 4i
- 3 - 4i
- -3 + 4i
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