In an equilateral triangle ABC if , then

Given in equilateral triangle ABC if AD BC.



We know that the Pythagoras theorem state that in a right angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.


Now, in right triangle ABD,


AB2 = AD2 + BD2


AB2 = AD2 + ( � BC)2 [ BD = �BC]


AB2 = AD2 + ( � AB)2 [ AB = BC]


AB2 = AD2 + ( �AB)2


3AB2 = 4AD2

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