Question

find the answer for this question

Answer 1

in triangle obc and oad
oa=ob(
od=oc(given)
angle cob =aod(vertically opp. ang.)
both triangle is congruent by sas
ad=bc(by c.p.c.t)
ad ll bc

Answer 2

In triangles AOD and BOC
OA=OB [GIVEN]
OD=OC [GIVEN]
angleAOD=angleBOC [VERTICALLY OPPOSITE ANGLES]
Hence by SAS congruency triangle AOD congruent triangle BOC

AngleB=AngleA [C.P.C.T]

BUT THESE ARE ALTERNATE ANGLES AND WHEN ALTERNATE ANGLES ARE EQUAL,THE LINES ARE PARALLEL

HENCE AD||BC .

$proved$
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