Q3 of 28 Page 112

The median AD, BE and CF in a ΔABC intersect at point G. Prove that


[Hint :AG + BG > AB]



As we know that in a triangle, sum of any two sides is always greater than the third side.


So, in ∆AGB,


AG+GB>AB…………….(1)


Also, AD=AG+GD


And BE=BG+GE


As we know that if the medians in a triangle intersect at a point then the point is the centroid of the triangle and the centroid divides the median in 2:1 ratio.


Here, G is the centroid of the ∆ABC.


So, AG:GD=2:1 and BG:GE=2:1






AD=3GD…………………..(2)


And AG=2GD…………………(3)


Dividing equation (2) by (3)




……………….(4)


Again,





BE=3GE…………………..(2)


And BG=2GE…………………(3)


Dividing equation (2) by (3)




……………….(5)


Putting the value of AG and BG in equation (1)


AG+BG>AB





Proved.


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