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  Short cut for finding circumcentre when three vertices are given   Awaiting Review for Nickels
Tagged with:    [Post New]posted on 14 Jul 2008 21:30:35 IST    

Ex: Find the circumcentre of the triangle formed by the points (-2,3) (2,-1) and (4,0)


Shift the origin to (-2,3) then the transformed vertices are (0,0) (4,-4) (6,-3)


2x1      2y1       -(x12 +y12)      2x1


2x2      2y2       -(x22 +y22)      2y2


      1        2                  3


Circumcentre = (2/1 , 3/1)   Where 1=(2x1)(2y2) - (2x2)(2y1)


In the above example we get


8   -8   -32   8                                 simplify the row if possible the we get    1   -1   -4     1


12  -6  -45   12                                                                                                      4   -2   -15   4


 


=  {(-1)(-15) - (-2)(-4)/(-2) - (-4) ,  (-4)(4) - (-15)(1)/(-2) - (-4)}


= {7/2 , -1/2}


 


But we hav to transform bak the equation to origin


Circum centre = {7/2+(-2), -1/2+3)} = {3/2 , 5/2)


 


Last step can be omitted if the given vertices are in the form of (0,0) (x1,y1) (x2,y2)

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smilingbharat (79)

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