QUESTION IMAGE
Question
quadrilateral abcd is a parallelogram. complete the statements to prove that \\( \overline { a b } \cong \overline { c d } \\) and \\( \overline { b c } \cong \overline { a d } \\).
| statement | reason |
|---|---|
| \\( \overline { a b } \parallel \overline { c d } \\) and \\( \overline { b c } \parallel \overline { a d } \\) | definition of a parallelogram |
| draw \\( \overline { a c } \\). \\( \overline { a c } \\) is a transversal that intersects two pairs of parallel lines, \\( \overline { a b } \\) and \\( \overline { c d } \\) and \\( \overline { a d } \\) and \\( \overline { b c } \\). | drawing a line segment |
| \\( \angle c a b \cong \angle a c d \\) and \\( \angle b c a \cong \angle c a d \\) | |
| \\( m \angle c a b = m \angle a c d \\) and \\( m \angle b c a = m \angle c a d \\) | congruent angles have equal measures. |
| \\( \overline { a c } = \overline { a c } \\) | |
| \\( \delta a b c \cong \delta c d a \\) | |
| \\( \overline { a b } \cong \overline { c d } \\) and \\( \overline { b c } \cong \overline { a d } \\) | corresponding sides of congruent triangles are congruent. |
Step1: Recall the Alternate Interior Angles Theorem
When a transversal intersects two parallel lines, alternate interior angles are congruent. Here, since \(\overline{AB}\parallel\overline{CD}\) and \(\overline{AC}\) is a transversal, \(\angle CAB\) and \(\angle ACD\) are alternate interior angles. Also, since \(\overline{BC}\parallel\overline{AD}\) and \(\overline{AC}\) is a transversal, \(\angle BCA\) and \(\angle CAD\) are alternate interior angles.
Step2: Use the ASA (Angle - Side - Angle) Congruence Criterion
We know that \(\angle CAB\cong\angle ACD\), \(\overline{AC}=\overline{AC}\) (reflexive property of equality), and \(\angle BCA\cong\angle CAD\). So, by the ASA congruence criterion, \(\triangle ABC\cong\triangle CDA\).
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The reason for \(\angle CAB\cong\angle ACD\) and \(\angle BCA\cong\angle CAD\) is the Alternate Interior Angles Theorem. The reason for \(\triangle ABC\cong\triangle CDA\) is the ASA (Angle - Side - Angle) congruence criterion.