We are given the perimeter of a square. Since a square has all of the sides of the same length the perimeter is, therefore:
[tex]P=4l[/tex]Where "l" is the length of the side. Solving for "l" by dividing both sides by 4:
[tex]\frac{P}{4}=l[/tex]Replacing the value of "P":
[tex]\frac{56}{4}=l[/tex]Solving the operations:
[tex]l=14[/tex]The length of the diagonal of a square is given by:
[tex]d=l\sqrt[]{2}[/tex]Replacing the value of the length we get:
[tex]d=14\sqrt[]{2}[/tex]Solving the operation:
[tex]d=19.8[/tex]Therefore, the length of the diagonal is 19.8 cm.
