The diagonal of a square is 18 cm. What is the length of its side?

The correct answer is Option (2) → \(9\sqrt{2}\) cm

The diagonal of a square of side \(a\) is \(a\sqrt{2}\) (Pythagoras on two sides), so \(a=\frac{\text{diagonal}}{\sqrt{2}}\).

• \(a\sqrt{2}=18\)

• \(a=\displaystyle\frac{18}{\sqrt{2}}=\frac{18\sqrt{2}}{2}=9\sqrt{2}\) cm