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Question 1045545:  show in a new way that the points (-1 -2), (5 4), (-3 0) are the vertices of a right triangle 
 Found 3 solutions by  ikleyn, blaser411, robertb: Answer by ikleyn(52903)      (Show Source): 
You can  put this solution on YOUR website! . 
1.  Calculate the length of each of the tree sides of the triangle, using the formula for the distance between the points in a coordinate plane.
2.  Then check that the square of the longest of the three sides is the sum
    of squares of the two other sides (Pythagorean equality).
 
I don't know what the words "in a new way" mean in this context.
 
 
 
 Answer by blaser411(1)      (Show Source):  Answer by robertb(5830)      (Show Source): 
You can  put this solution on YOUR website! A vector associated with the points (-1,-2) and (5,4) is < 5--1, 4--2 > = < 6, 6 >.
 
A vector associated with the points (-1,-2) and (-3,0) is < -3--1,0--2 > = < -2,2 >.
 
Two vectors are perpendicular (or orthogonal) if their dot product is 0, 
 
< 6,6 >*<-2,2 > = -12 + 12 = 0.
 
This, however, is not a new way, just a little level higher.  
 
Another way of showing this perpendicularity, but still not a "new" way, just a level lower, is  
getting the slope of the line passing through (-1,-2) and  
(5,4) and comparing this with the slope of the line passing through (-1,-2)  
and (-3,0). 
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