The area of the square is, of course, 1 square unit
Each of equilateral triangles has a side of 1, so their total area is
4 (1/2) * 1^2 * sin (60) = 2*√3/2 = √3 square units
The other 4 triangles have two sides of 1 and an included angle between these sides of
[360 - 90 - 60 - 60 ] = 150°
So...their area is
4 (1/2) * 1^2 * sin (150) = 2 * (1/2) = 1 square unit
So...the area of the larger square is ( 1 + 1 + √3) = [ 2 + √3 ] units^2