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#### 21.2.4 Complex Numbers

Complex numbers are the set of numbers that describe all possible points in a two-dimensional space. The two coordinates of a particular point in this space are known as the real and imaginary parts of the complex number that describes that point.

In Guile, complex numbers are written in rectangular form as the sum of their real and imaginary parts, using the symbol `i` to indicate the imaginary part.

```3+4i
=>
3.0+4.0i

(* 3-8i 2.3+0.3i)
=>
9.3-17.5i
```

Guile represents a complex number as a pair of numbers both of which are real, so the real and imaginary parts of a complex number have the same properties of inexactness and limited precision as single real numbers.

 complex? x Scheme Procedure scm_number_p (x) C Function
 Return `#t` if x is a complex number, `#f` otherwise. Note that the sets of real, rational and integer values form subsets of the set of complex numbers, i. e. the predicate will also be fulfilled if x is a real, rational or integer number.