Complex Numbers

  • Complex numbers are numbers of the form a + bi, where a and b are real numbers and i is the imaginary unit, which is defined by i² = -1.
  • Complex numbers can be added, subtracted, multiplied, and divided using the rules of algebra.
  • The modulus of a complex number is the distance from the origin to the point in the complex plane that represents the number.
  • The amplitude of a complex number is the angle that the line from the origin to the point in the complex plane that represents the number makes with the positive real axis.
  • The conjugate of a complex number is obtained by changing the sign of the imaginary part.

Important Formulas to Remember in these Complex Numbers


  • \( z=a+bi \), where \( a,b\in\mathbb{R} \) and \( i^2=-1 \).
  • \( |z|=\sqrt{a^2+b^2} \) is the modulus of the complex number.
  • \( \text{Arg}(z)=\theta \), where \( \theta \) is the argument of the complex number, i.e. the angle it makes with the positive real axis in the complex plane.
  • \( \text{Re}(z)=a \) and \( \text{Im}(z)=b \) are the real and imaginary parts of the complex number, respectively.
  • \( \overline{z}=a-bi \) is the complex conjugate