We can notice the triangle on the square, hypotenuse is 8m and the base is half of the lengt of the square we will name it x
then
we can use pythagoras to solve
where a and b aer sides of the triangle and h the hypotenuse
replacing
the length of x is half of the side of the square then the side of the square is
each side of the square is 8v2 meters
Area
we use formula of the area
area of the square is 128 square meters
Perimeter
we use formula of the perimeter
perimeter of the square is 32v2 meters