G3.3 In Figure 1, a square of side length $Q \mathrm{~cm}$ is inscribed in a semi-circle of radius $2 \mathrm{~cm}$. Find the value of $Q$.
$Q^{2}+\left(\frac{Q}{2}\right)^{2}=4$ (Pythagoras' Theorem) $5 Q^{2}=16$
$$
Q=\frac{4}{\sqrt{5}}=\frac{4 \sqrt{5}}{5}
$$