6.1 Distance between Two Points

6.1 Distance between Two Points
(x1, y1) and (x2, y2) are two points on a coordinate plane as shown below. BC is parallel to the x-axis and AB is parallel to the y-axis.  Hence  ∆ ABC = 90°.


Distance between Point A and C =  



Example:
Find the distance between the points P (2, 2) and Q (–4, –5).

Solution:
Let P (2, 2) = (x1, y1 ) and Q (–4, –5) = (x2, y2 ).

Distance of  P Q = ( x 2 x 1 ) 2 + ( y 2 y 1 ) 2 = ( 4 2 ) 2 + ( 5 ( 2 ) ) 2 = 36 + 9 = 45 = 9 × 5 = 3 5  or  ( 6.71 )