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Distance Formula

In the coordinate plane, you can use the Pythagorean Theorem to find the distance between any two points.

The distance between the two points (x1,y1) and (x2,y2) is given by the distance formula.


     

 

 

Example:

To find the distance between the points P(2, 3) and Q(1, 1). We can sketch the right-angled triangle PQR with PQ as the hypotenuse.

 

 

Solution:
Using Pythagoras theorem: PQ2 = (2 – 1)2 + (3 –1)2
   Þ PQ =

 

 

In general, the distance between two points P(x1,y1) and Q(x2,y2) is given by the distance formula:

Example:
Find the distance between the points A(1, 2) and B(-3, -2).

Solution:
Using the distance formula:
Distance =
                   = 5.66 (correct to 2 decimal places)

 

 

The following video gives another example of using the distance formula.

 

 

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Useful Links:
Mathworld - Coordinate Geometry
Math.com - Coordinate Geometry
 
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