CD is a perpendicular from C to AB. Prove that triangles ACD and CBD are both simlar to triangle ABC. (See attached image) I can prove corresponding angles are congruent very easily for ABC and CBD. For example, angle A = angle A for both ABC and ACD. Also, angle D = angle C since ABC is a right triangle and CD is perpendicular to AB. Lastly, angle ACD = 90 - angle DAC and angle ABC = 90 - angle DAC. Therefore, angle ACD = angle ABC. Thus all three corresponding angles are congruent. For showing that the sides are proportional, I have no clue. What confuses me is what c represents. I am guessing it is supposed to represent AB. If it does, then what in the world is AD supposed to be? Or if c represents AD then what is DB supposed to be? Thanks for all your help. Tell me if I have started on the wrong foot or if I am way off in my approach. Any feedback is welcome.