Find the area of a square

Diagonal of square = d = 14 cm
Relation between side and diagonal: d = $ a\sqrt{2} $
$ a = \frac{d}{\sqrt{2}} = \frac{14}{\sqrt{2}} = 7\sqrt{2} $
Area of square = $ a^2 $
$ = (7\sqrt{2})^2 $
= 98
${98 \text{ cm}^2} $