Question

find the height of an equilateral triangle whose side is 6 units

Answer 1

Use Pythagoras Theorem.
let height be h units
Then by Phythagoras theorem,
a²=h²+(a/2)²
h²=a²-(a/2)²
h²=a²-a²/4
h=√3 a/2
Then, Height of given triangle = √3 ×6/2=3√3 units

Note: You can directly put the values of (a) and (a/2) when using Pythagoras theorem