Question

The figure below shows a parallelogram ABCD. Side AB is parallel to side DC, and side AD is parallel to side BC. A student wrote the following sentences to prove that parallelogram ABCD has two pairs of opposite sides equal. Which statement best describes a flaw in the student's proof?

a. Angle ABD is congruent to angle CBD because they are vertical angles, not alternate interior angles.
b. Angle ABD is congruent to angle CBD because they are corresponding angles, not alternate interior angles.
c. Triangles ABD and CDB are congruent by the ASA postulate instead of the SAS postulate.
d. Triangles ABD and CBD are congruent by the SSS postulate instead of the SAS postulate.

Answer 1

The flaw in the student's proof is that it incorrectly uses the SSS postulate instead of the SAS postulate.

Step-by-step explanation:

The flaw in the student's proof is described in option d. Triangles ABD and CBD are congruent by the SSS postulate instead of the SAS postulate.

The student's proof incorrectly uses the SSS (Side-Side-Side) postulate to prove that the triangles are congruent, when it should use the SAS (Side-Angle-Side) postulate. So, the statement in option d best describes the flaw in the student's proof.