Definition and Cartesian form

A complex number arises by introducing a new symbol $i$ with $i^2=-1$ and writing every number in the form $z=a+ib$. In this section we define the real part and the imaginary part, we learn to add, multiply and divide in Cartesian form using the conjugate, and we introduce the modulus as the “length” of a complex number.

• Complex number and Cartesian form
• Operations in Cartesian form
• Modulus of a complex number