In an equilateral triangle ABC if , then AD2 =
Given in equilateral triangle ABC, 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 ADC,
⇒ AC2 = AD2 + DC2
⇒ BC2 = AD2 + DC2 [∵ AC = BC]
⇒ (2DC)2 = AD2 + DC2 [∵ BC = 2DC]
⇒ 4DC2 = AD2 + DC2
⇒ 3DC2 = AD2
∴ 3CD2 = AD2