Question

Prove that area of equilateral triangle =3 by 4 Side²

Answer 1

Answer:

$3 \div 4 {x}^{2}$

Answer 2

Step 1: Since all the 3 sides of the triangle are same,

AB = BC = CA = a

Step 2: Find the altitude of the △ABC.  

Draw a perpendicular from point A to base BC, AD ⊥ BC

By using Pythagoras theorem

In △ ADC

h2 = AC2 - DC2

= a2 - (a2)2 [Because, DC = a2 ]

= a2 - a24

h = 3√a2

Step 3: We know that, Area of a triangle = 12 * Base * Height

= 12 * a * 3√a2

= 3√4a2

The area of a equilateral triangle = 3√4a2.