Use ruler and compass only for answering this question.
Draw a circle of radius $4\mathrm{cm}$. Mark the centre as $\mathrm{O}$. Mark a point $\mathrm{P}$ outside the circle at a distance of $7\mathrm{cm}$ from the centre. Construct two tangents to the circle from the external point $\mathit{P}$.
Measure and write down the length of any one tangent.