A child's temporary teeth, or milk teeth, start getting replaced by permanent teeth around the age of 5 to 6 years. This process is a part of normal childhood development.
In the adjoining figure, $\triangle CAB$ is a right triangle, right angled at A and $AD \perp BC$. Prove that $\triangle ADB \sim \triangle CDA$. Further, if $BC = 10$ cm and $CD = 2$ cm, find the length of AD.