Observe the figure given.
Given: ABCD is a parallelogram.
To prove: ABCD is a rhombus
Statement
1. ABCD is a parallelogram. AC bisects [tex]\angle BCD, \angle BAD[/tex].
Reason: Given
2. [tex]\angle 1 \cong \angle 2, \angle 3 \cong \angle 4[/tex]
Reason: Definition of an angle bisector
3. [tex]AC \cong AC[/tex]
Reason: Reflexive property of congruence
4. [tex]\Delta ABC \cong \Delta ADC[/tex]
Reason: ASA Postulate
5. [tex]AB \cong AD, BC \cong DC[/tex]
Reason: corresponding parts of congruent triangles are equal.
6. [tex]AB \cong CD, BC \cong AD[/tex]
Reason: Opposite sides of the parallelogram are congruent.
7. [tex]AB \cong AD \cong BC \cong CD[/tex]
Reason: Transitive property of congruence
8. ABCD is a rhombus
Reason: Definition of rhombus