a - length of side of a square
t - length of side of a triangle
The perimeter of a square: 
The perimeter of a triangle: 
We have the area of a triangle: 
The formula of an area of an equilateral trinagle: 
Substitute:
<em>multiply both sides by 4</em>
<em>divide both sides by
</em>

The perimeter of a triangle: 
Substitute to the formula of a perimeter of a square:
<em>divide both sides by 4</em>

The formula of a diagonal of a square: 
Substitute:
