Answer:
13cm
Explanation:
Let the length of each side be x;
Using the pythagoras theorem
l² = x² + x²
l is the length of the diagonal
l² = 2x²
19² = 2x²
361 = 2x²
x² = 361/2
x² = 180.5
x =√180.5
x = 13
hence the length of each side of the square is closest to 13cm