All the steps were correct except the final statement. The
mistake was in Line 6.
Line 6 triangle ABC is congruent to triangle EFD by
SAS.
<span>This does not follow. The SAS postulate states
that if two sides and the included angle of one triangle is congruent to two sides
and the included angle of another triangle. The student only proved that one side
of the triangle (AC) is congruent to the side of another triangle (EF) .</span>
