## Elementary Geometry for College Students (6th Edition)

The proof is in the following form: Column 1 of proof; Column 2 of proof. Thus, we have: 1. ADC is a right angle, and CDB is a right angle; Given 2. The altitude of triangle ABC is CD; definition of an altitude 3. CDA is similar to triangle CDB; the altitude of the hypotenuse of a right triangle forms to similar triangles. 4. $\frac{AD}{CD} = \frac{CD}{DB}$; CSSTP