The altitude of an equilateral triangle of side 2 3 cm is :

Answer: Option D

Let ABC be the equilateral triangle and AD be the altitude on base BC

In an equilateral triangle, the altitude and the median coincide.
So, BC = DC = $$\left(\frac{2\sqrt{3}}{2}\right)$$ cm = $$\sqrt{3}$$ cm
Let the length of the altitude AD be x cm
Then, in right angled ΔADB,
AB² = AD² + BD²
⇒ $${\left(2\sqrt{3}\right)}^2$$  = x² + $${\left(\sqrt{3}\right)}^2$$
⇒ x² = (12 - 3)
⇒ x² = 9
⇒ x = 3 cm