Q10 of 184 Page 10

Find the length of the medians of the triangle whose vertices are (-1,3),(1,-1) and (5,1).


Let the given points of a triangle be A(-1, 3), B(1, -1) and C(5,1)


Let D, E and F are the midpoints of the sides BC, CA and AB respectively.


The coordinates of D are:




D = (3, 0)


The coordinates of E are:




E = (2, 2)


The coordinates of F are:




F = (0, 1)


Now, we have to find the lengths of the medians.


d(A,D) = √(x2 – x1)2 + (y2 – y1)2


= √{3 – (-1)2} + {0 – 3}2


= √(3 + 1)2 + (-3)2


= √16 + 9


= √25


= 5 units


d(B,E) = √(x2 – x1)2 + (y2 – y1)2


= √(2 – 1)2 + {2 – (-1)}2


= √(1)2 + (2 + 1)2


= √1 + 9


= √10 units


d(C,F) = √(x2 – x1)2 + (y2 – y1)2


= √(5 – 0)2 + {1 – 1}2


= √(5)2 + (0)2


= √25


= 5 units


Hence, the length of the medians AD, BE and CF are 5, √10, 5 units respectively.


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