It has been proven that ABCD is a parallelogram by using the single opposite side pair theorem.
What is a parallelogram?
A parallelogram can be defined as a type of polygon (quadrilateral) that has two equal pairs of parallel sides.
The single opposite side pair theorem.
Basically, the opposite sides of a parallelogram ABCD are always equal and as such we have:
Also, if a pair of opposite sides of a polygon (quadrilateral) is both congruent and parallel, then it is considered as a parallelogram based on the following:
- AD≅BC [tex]\rightarrow[/tex] (given)
- AD║BC [tex]\rightarrow[/tex] (given)
- ∠DAC and ∠BCA are alternate interior angles [tex]\rightarrow[/tex] (def. of alt. interior angles).
- ∠DAC ≅ ∠BCA [tex]\rightarrow[/tex] (alternate interior angle theorem).
- AC ≅ AC [tex]\rightarrow[/tex] (reflexive property).
- ΔDAC ≅ ΔBCA [tex]\rightarrow[/tex] (side-angle-side = SAS).
- AB ≅ CD [tex]\rightarrow[/tex] (CPCTC = corresponding parts of congruent triangles are congruent).
- ABCD is a parallelogram [tex]\rightarrow[/tex] (parallelogram side theorem)
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