ABCD is a quadrilateral where AC is a diagonal cutting ABCD into 2 triangles, triangle ABC and triangle CDA.

AB is parallel to DC and AB=DC.

(a)Is angle BAC equal to angle DCA?why?

(b) is triangle ABC conguent to triangle CDA?why?

(c) is angle B equal to angle D?why?


If AB || CD and AB= CD then AD  =BC because distance between the ends points of finite and equal parallel lines is same.
So ABCD can be rectangle and square and parallelogram,
 
BAC=DCA Alternate interior angle as ABCD and AC is transversal

In triangle ABC and DCA, AC=ACAB=CD givenACD=CAB provedSO  ABC DCA by SAS congruency

SInce it can be rectangle, square or parallelogram hence angle B will be equal to angle D. 

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