Find the other end point of a line with given one end and mid

Namachila November 19, 2025

0 0 3 minutes read

Given a midpoint of line(m1, m2) and one coordinate of a line (x1, y1), find the other end point(x2, y2) of a line.

Examples:

Input  : x1 = –1, y1 = 2, and 
         m1 = 3, m2 = –6
Output : x2 = 7, y2 = 10

Input  : x1 = 6.4, y1 = 3 and 
         m1 = –10.7, m2 = 4
Output : x2 = 3, y2 = 4

The Midpoint Formula: The midpoint of two points, (x1, y2) and (x2, y2) is the point M found by using:
M=((x1+x2)/2, (y1+y2)/2),

We have need of a (x2, y2) so we modifies the formula

          m1 = ((x1+x2)/2),  m2 = ((y1+y2)/2)
          2*m1 = (x1+x2),  2*m2 = (y1+y2)
          x2 = (2*m1 - x1),  y2 = (2*m2 - y1)

C++

// CPP program to find the end point of a line 
#include <iostream> 
using namespace std; 
  
// CPP function to find the end point of a line 
void otherEndPoint(int x1, int y1, int m1, int m2) 
{ 
    // find end point for x coordinates 
    float x2 = (float)(2 * m1 - x1); 
  
    // find end point for y coordinates 
    float y2 = (float)(2 * m2 - y1); 
  
    cout << "x2 = " << x2 << ", "
         << "y2 = " << y2; 
} 
  
// Driven Program 
int main() 
{ 
    int x1 = -4, y1 = -1, m1 = 3, m2 = 5; 
    otherEndPoint(x1, y1, m1, m2); 
    return 0; 
} 

Java

// Java program to find the end point of a line 
class GFG { 
      
    // Java function to find the end point 
    // of a line 
    static void otherEndPoint(int x1, int y1,  
                               int m1, int m2) 
    { 
        // find end point for x coordinates 
        float x2 = (float)(2 * m1 - x1); 
      
        // find end point for y coordinates 
        float y2 = (float)(2 * m2 - y1); 
      
        System.out.println("x2 = " + x2 + ", "
                               + "y2 = " + y2); 
    } 
      
    // Driven Program 
    public static void main(String args[]) 
    { 
        int x1 = -4, y1 = -1, m1 = 3, m2 = 5; 
        otherEndPoint(x1, y1, m1, m2); 
    } 
} 
  
// This code is contributed by JaideepPyne. 

Python3

# Python3 program to find the end 
# point of a line 
  
# function to find the end point 
# of a line 
def otherEndPoint(x1, y1, m1, m2): 
      
    # find end point for x coordinates 
    x2 = (2 * m1 - x1) 
  
    # find end point for y coordinates 
    y2 = (2 * m2 - y1) 
  
    print ("x2 = {}, y2 = {}" 
               . format(x2, y2)) 
  
# Driven Program 
x1 = -4
y1 = -1
m1 = 3
m2 = 5
otherEndPoint(x1, y1, m1, m2) 
  
# This code is contributed by  
# Manish Shaw (manishshaw1) 

C#

// C# program to find the 
// end point of a line 
using System; 
  
class GFG { 
      
    // function to find the  
    // end pointof a line 
    static void otherEndPoint(int x1, int y1,  
                              int m1, int m2) 
    { 
          
        // find end point for x coordinates 
        float x2 = (float)(2 * m1 - x1); 
      
        // find end point for y coordinates 
        float y2 = (float)(2 * m2 - y1); 
      
        Console.WriteLine("x2 = " + x2 + ", "
                          + "y2 = " + y2); 
    } 
      
    // Driver Program 
    public static void Main(String []args) 
    { 
        int x1 = -4, y1 = -1, m1 = 3, m2 = 5; 
        otherEndPoint(x1, y1, m1, m2); 
    } 
} 
  
// This code is contributed by nitin mittal. 

PHP

<?php 
// php program to find the end point of a line 
  
// PHP function to find the end point of a line 
function otherEndPoint($x1, $y1, $m1, $m2) 
{ 
      
    // find end point for x coordinates 
    $x2 = (2 * $m1 - $x1); 
  
    // find end point for y coordinates 
    $y2 = (2 * $m2 - $y1); 
  
    echo "x2 = " . $x2 . ", y2 = " . $y2 ; 
} 
  
// Driven Program 
    $x1 = -4; $y1 = -1; $m1 = 3; $m2 = 5; 
    otherEndPoint($x1, $y1, $m1, $m2); 
  
// This code is contributed by nitin mittal. 
?> 

Javascript

<script> 
  
// Javascript program to find the  
// end point of a line 
  
// Function to find  
// the end point of a line 
function otherEndPoint(x1, y1, m1, m2) 
{ 
      
    // Find end point for x coordinates 
    let x2 = 2 * m1 - x1; 
  
    // Find end point for y coordinates 
    let y2 = 2 * m2 - y1; 
  
    document.write("x2 = " + x2 + ", " +  
                   "y2 = " + y2); 
} 
  
// Driver code  
let x1 = -4, y1 = -1, m1 = 3, m2 = 5; 
  
otherEndPoint(x1, y1, m1, m2); 
  
// This code is contributed by jana_sayantan 
      
</script>

Output:

x2 = 10, y2 = 11

Time Complexity:O(1)

Auxiliary Space:O(1)

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