Complex numbers in Octave

In this lesson I'll show you how to write complex numbers in Octave using a practical example.

There are two ways to write a complex number in Octave.

You can use the function complex(a,b) where a is the real part and b is the imaginary part.

>> complex(3,4)

Alternatively, you can write the complex number in algebraic form using the imaginary unit i or j.

>> 3+4i

Let me give you a practical example.

Go to Octave and type the complex number a=3-4i. Then press enter.

>> a = 3+4i.

The software recognizes that it is a complex number in algebraic form.

The complex number 3+4i is assigned to the variable a.

Note. You can also write the symbol for the imaginary unit using the letter j (e.g. 3+4j). Octave recognizes the complex number. However, the software automatically transforms the imaginary unit using the letter i (e.g. 3+4i).

Now type another complex number b=2+5i and press enter.

>> b = 2+5i

At this point there are two complex variables in memory.

You can perform any mathematical operation with the two numbers (e.g. addition, subtraction, multiplication, division).

For example, you can add the two complex numbers

>> a+b
ans = 8 + 5i

You can subtract the complex numbers

>> a-b
ans = -2 - 1i
>> b-a
ans = 2 + 1i

You can multiply the complex numbers

>> a*b
ans = 9 + 19i

You can also calculate the square of a complex number

>> a^2
ans = 5 + 12i

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