It seems the first line has to be
1. AB=CD and AD=CB 1. given
2. AC=AC 2. Reflexivity (things are equal to themselves)
3 [tex] \triangle [/tex] ACB [tex]\cong[/tex] [tex] \triangle[/tex] CAD 3. SSS
4. [tex] \angle [/tex] 1 = [tex] \angle [/tex] 4. Corresponding parts of congruent triangles
5 DC || AB 5. Congruent alternate traversal angles imply parallel lines
