Question

in a parrallogram abcd , bc=ad and angle a is 90 than show it is a sequre.

Answer 1

given:abcd is a parallelogram where bc=ad
        angle a=90degree
rtp: abcd is a square
construction:db is joined
proof:in triangle adb &bcd
         ad=bc
         bd is the common arm
       &abd=alternate angle bdc
     so triangle abd congruent bcd(sas)
     therefore,ab=dc(cpct)
so,in the parralelogram abcd the four sides are equal
therefore abcd is a square
           THUS PROVED

Answer 2

Given:parallelogram abcd, a=90
to prove : abcd is a square
proof: in   triangles abd and bcd, 
ad=bc- s
cdb=dba-a(alternate angles)
ab=dc -s
by sas congruence rule triangle abd≈bcd.
since two pair of opposite sides are equal and one angle is 90, it is a square