A step that contains an error is justification 4.
Statement Justification
4.
= AC × AD 4. AB ÷ AD = AC ÷ AB because triangle ABC is similar to triangle ABD.
The Right Triangles Similarity Theorem states that when the altitude of a triangle is drawn to the hypotenuse of a right angled triangle, then, the two triangles that are formed would be similar to each other, as well as the original triangle.
By applying the Right Triangles Similarity Theorem, we can reasonably and logically deduce that both triangle ABC and triangle BDA are similar triangles.
Since triangle ABC is similar to triangle BDA, we have the following proportions;
AB/AD = AC/AB
= AC × AD