8. In right $\triangle A B C, C D$ is the altitude to hypotenuse $A B$. If $A C=12$ and $A D=5$, find $D B$. 12

Step 1 ：Given a right triangle ABC, with CD as the altitude to the hypotenuse AB. The lengths of AC and AD are given as 12 and 5 respectively. We are asked to find the length of DB.

Step 2 ：In a right triangle, the length of the altitude to the hypotenuse is the geometric mean of the lengths of the two segments of the hypotenuse. This gives us the equation \(AD^2 = AC * DB\).

Step 3 ：Substituting the given values into the equation, we get \(5^2 = 12 * DB\).

Step 4 ：Solving for DB, we get \(DB = \frac{25}{12}\).

Step 5 ：Final Answer: \(DB = \boxed{\frac{25}{12}}\)