Roots of Unity

Given a small integer n, print all the n'th roots of unity up to 6 significant digits. We basically need to find all roots of equation xⁿ - 1.

Examples: 

Input :  n = 1
Output : 1.000000 + i 0.000000
x - 1 = 0 , has only one root i.e., 1

Input :  2
Output : 1.000000 + i 0.000000
    -1.000000 + i 0.000000
x2 - 1 = 0 has 2 distinct roots, i.e., 1 and -1 

Any complex number is said to be root of unity if it gives 1 when raised to some power. 
nth root of unity is any complex number such that it gives 1 when raised to the power n.  

Mathematically, 
An nth root of unity, where n is a positive integer 
(i.e. n = 1, 2, 3, …) is a number z satisfying the
equation 

z^n  = 1
or , 
z^n - 1 = 0

We can use the De Moivre's formula here ,  

( Cos x + i Sin x )^k = Cos kx + i Sin kx

Setting x = 2*pi/n, we can obtain all the nth roots 
of unity, using the fact that Nth roots are set of 
numbers given by,

Cos (2*pi*k/n) + i Sin(2*pi*k/n)
Where, 0 <= k < n

Using the above fact we can easily print all the nth roots of unity ! 

Below is the program for the same. 

// C++ program to print n'th roots of unity
#include <bits/stdc++.h>
using namespace std;

// This function receives an integer n , and prints
// all the nth roots of unity
void printRoots(int n)
{
    // theta = 2*pi/n
    double theta = M_PI*2/n;

    // print all nth roots with 6 significant digits
    for(int k=0; k<n; k++)
    {
        // calculate the real and imaginary part of root
        double real = cos(k*theta);
        double img = sin(k*theta);

        // Print real and imaginary parts
        printf("%.6f", real);
        img >= 0? printf(" + i "): printf(" - i ");
        printf("%.6f\n", abs(img));
    }
}

// Driver function to check the program
int main()
{
    printRoots(1);
    cout << endl;
    printRoots(2);
    cout << endl;
    printRoots(3);
    return 0;
}

// Java program to print n'th roots of unity
import java.io.*;

class GFG {

// This function receives an integer n , and prints
// all the nth roots of unity
static void printRoots(int n)
{
    // theta = 2*pi/n
    double theta = 3.14*2/n;

    // print all nth roots with 6 significant digits
    for(int k=0; k<n; k++)
    {
        // calculate the real and imaginary part of root
        double real = Math.cos(k*theta);
        double img = Math.sin(k*theta);

        // Print real and imaginary parts
        System.out.println(real);
        if (img >= 0)
            System.out.println(" + i ");
        else
            System.out.println(" - i ");
        System.out.println(Math.abs(img));
    }
}

// Driver function to check the program
public static void main (String[] args)
{
    printRoots(1);
    //System.out.println();
    printRoots(2);
    //System.out.println();
    printRoots(3);
}
}
// This code is contributed by Raj

# Python3 program to print n'th roots of unity

import math

# This function receives an integer n , and prints
# all the nth roots of unity
def printRoots(n):

    # theta = 2*pi/n
    theta = math.pi * 2 / n

    # print all nth roots with 6 significant digits
    for k in range(0, n):

        # calculate the real and imaginary part of root
        real = math.cos(k * theta)
        img = math.sin(k * theta)

        # Print real and imaginary parts
        print(real, end=" ")
        if(img >= 0):
            print(" + i ", end=" ")
        else:
            print(" - i ", end=" ")
        print(abs(img))


# Driver function to check the program
if __name__=='__main__':
    printRoots(1)
    printRoots(2)
    printRoots(3)

# This code is contributed by
# Sanjit_Prasad

// C# program to print n'th roots of unity 
using System;

class GFG { 

// This function receives an integer n , and prints 
// all the nth roots of unity 
static void printRoots(int n) 
{ 
    // theta = 2*pi/n 
    double theta = 3.14*2/n; 

    // print all nth roots with 6 significant digits 
    for(int k=0; k<n; k++) 
    { 
        // calculate the real and imaginary part of root 
        double real = Math.Cos(k*theta); 
        double img = Math.Sin(k*theta); 

        // Print real and imaginary parts 
        Console.Write(real); 
        if (img >= 0) 
            Console.Write(" + i "); 
        else
            Console.Write(" - i "); 
        Console.WriteLine(Math.Abs(img)); 
    } 
} 

// Driver function to check the program 
static void Main() 
{ 
    printRoots(1); 
     
    printRoots(2); 
     
    printRoots(3); 
} 
} 
// This code is contributed by mits

<?php
// PHP program to print n'th roots of unity

// This function receives an integer n, 
// and prints all the nth roots of unity
function printRoots($n)
{
    
    // theta = 2*pi/n
    $theta = pi() * 2 / $n;

    // print all nth roots with 6
    // significant digits
    for($k = 0; $k < $n; $k++)
    {
        // calculate the real and imaginary 
        // part of root
        $real = cos($k * $theta);
        $img = sin($k * $theta);

        // Print real and imaginary parts
        print(round($real, 6));
        $img >= 0 ? print(" + i "): print(" - i ");
        printf(round(abs($img), 6) . "\n");
    }
}

// Driver Code
printRoots(1);
printRoots(2);
printRoots(3);

// This code is contributed by mits
?>

<script>
// javascript program to print n'th roots of unity

// This function receives an integer n , and prints
// all the nth roots of unity
function printRoots(n)
{
    // theta = 2*pi/n
    var theta = (3.14*2/n);

    // print all nth roots with 6 significant digits
    for(k = 0; k < n; k++)
    {
        // calculate the real and imaginary part of root
        var real = Math.cos(k*theta);
        var img = Math.sin(k*theta);

        // Print real and imaginary parts
        document.write(real.toFixed(6));
        if (img >= 0)
            document.write(" + i ");
        else
            document.write(" - i ");
        document.write(Math.abs(img).toFixed(6)+'<br>');
    }
}

// Driver function to check the program
printRoots(1);

//document.write('<br>');
printRoots(2);

//document.write('<br>');
printRoots(3);

// This code is contributed by shikhasingrajput 
</script>

Output: 

1.000000 + i 0.000000
1.000000 + i 0.000000
-1.000000 + i 0.000000
1.000000 + i 0.000000
-0.500000 + i 0.866025
-0.500000 - i 0.866025

References: Wikipedia