Question

solution of this question

Answer 1

here DBCE is an isoceles trapezium where BD = EC
by mid point theorem
DE// BC
so angle ADE = angle ABC .......(1)
and angle AED = angle ACB .......(2)
and angle ABC = angle ACB ( AB = AC ) .......(3)

angle EDB = 180 -x
angle DEC = 180-x ( linear pair )
angle ABC + angle DEC = x + 180-x = 180
since sum of opposite angles is 180 so it is concyclic