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# C++ Program to initialize and print a complex number

Complex numbers are a very fundamental concept in modern science, the concept is first
introduced in the early 17^{th} century. Complex numbers are of the form a + ib, where a and b
are real numbers. a is known as the real part and ib is known as the imaginary part of a
complex number. In C++, there is a class to represent complex numbers which is the
complex class. The complex class in C++ can represent and manipulate various operations
on complex numbers. We take a look at how to represent, initialize, and display complex
numbers.

## Initializing using the class constructor

To use the complex class, we have to import the complex library which can be imported or
included using the #include

### Syntax

double value1 = <double value>; double value2 = <double value>; complex <double> cno(value1, value2);

### Algorithm

Take input in two numerical variables.

Pass the two variables to the constructor of the complex number.

Display the complex number.

### Example

#include <iostream> #include <complex> using namespace std; //displays the complex number supplied void display(complex <double> c){ cout << "The complex number is: "; cout << real(c) << '+' << imag(c) << 'i' << endl; } //initializing the complex number complex<double> solve( double real, double img ){ complex<double> cno(real, img); return cno; } int main(){ //the real and the imaginary values are represented as double values double v1 = 10; double v2 = 7; //creating and displaying the complex number display(solve(v1, v2)); return 0; }

### Output

The complex number is: 10+7i

Any numerical data type can be used in place of the complex number variable's current type, which is double.

## Initializing using the assignment operator

We may also use the assignment operator to assign real and imaginary values to a complex number. Nevertheless, to do that, we must provide a number of the type "a + ib," where "a" and "b" are both numerical values. If the number is an integer, zeros are placed in the space after the decimal points. A decimal point must be used when writing the real portion "a." 10 must be written as 10.0, for instance.

### Syntax

//the real and imaginary parts have to be assigned as it is complex <double> cno = 15.0 + 6i;

### Algorithm

Take a new complex number object.

Assign a value to the object using the ‘a. + ib’ notation.

Display the complex number value.

### Example

#include <iostream> #include <complex> using namespace std; //displays the complex number supplied void display(complex <double> c){ cout << "The complex number is: "; cout << real(c) << '+' << imag(c) << 'i' << endl; } int main(){ //initializing a complex number object complex <double> cno = 15. + 6i; //displaying the complex number display(cno); return 0; }

### Output

The complex number is: 15+6i

## Displaying a complex number

Using the "real()" and "imag()" functions, the real and imaginary parts of a complex integer are displayed separately. The "real()" function shows the complex number's real portion, whereas the "imag()" function shows the complex number's imaginary portion. Here is a sample of that.

### Syntax

//displaying in the a + ib format complex<double> c; cout << real(c) << '+' << imag(c) << 'i' << endl;

### Algorithm

Take a new complex number object.

Assign the value to the object using the ‘a. + ib’ notation.

Display the complex number value.

### Example

#include <iostream> #include <complex> using namespace std; //displays the complex number supplied void display(complex <double> c){ cout << "The complex number is: "; cout << real(c) << '+' << imag(c) << 'i' << endl; } //initializing the complex number complex<double> solve( double real, double img ){ complex<double> cno(real, img); return cno; } int main(){ //the real and the imaginary values are represented as double values double v1 = 3; double v2 = 4; //creating and displaying the complex number display(solve(v1, v2)); return 0; }

### Output

The complex number is: 3+4i

### Conclusion

Complex numbers are needed for many different procedures across a wide range of
scientific disciplines. The C++ complex class, included in the header