The sum of perimeters of an equilateral traingle and a square is
.
Area of the square is 
Area of the equilateral traingle is 
Let us consider side of the equilateral triangle that produces minimum area is
.
Let us consider side of the square that produces minimum area is 
Total area : 
Sum of perimeters of an equilateral traingle and a square is
.
.

Substitute
in
.

Find the minimum area.
\
Differentiate on each side with respect to
.


.
Evaluate
.




The dimensions of the triangle minimum area is 
Substitute
in
.


.
The dimensions of the square minimum area is
.
The dimensions of the triangle for minimum area is
.
The dimensions of the square for minimum area is
.