Seth is using the figure shown below to prove Pythagorean Theorem using triangle similarity. In the given triangle ABC, angle A is 90° and segment AD is perpendicular to segment BC.

The figure shows triangle ABC with right angle at A and segment AD. Point D is on side BC.

Part A: Identify a pair of similar triangles.

Part B: Explain how you know the triangles from Part A are similar.

Part C: If DB = 9 and DC = 4, find the length of segment DA. Show your work.