Multiply $\frac{1}{2}$ times $\frac{2}{7}$ by multiplying numerator times numerator and denominator times denominator.
$$\frac{1\times 2}{2\times 7}\sqrt{14}\sqrt{21}$$
Cancel out $2$ in both numerator and denominator.
$$\frac{1}{7}\sqrt{14}\sqrt{21}$$
To multiply $\sqrt{14}$ and $\sqrt{21}$, multiply the numbers under the square root.
$$\frac{1}{7}\sqrt{294}$$
Factor $294=7^{2}\times 6$. Rewrite the square root of the product $\sqrt{7^{2}\times 6}$ as the product of square roots $\sqrt{7^{2}}\sqrt{6}$. Take the square root of $7^{2}$.
