In Fig.10.13, ADC = 130° and chord BC = chord BE. Find
CBE.
Consider BCO and
BEO
BC = BE as given.
BCO =
BEO (angles opposite to equal sides in a triangle are equal)
BO = BO (common sides)
BCO
BEO (SAS congruence)
CBO =
OBE (CPCT) …(i)
Now we know that ABCD is a Cyclic quadrilateral,
So, ADC +
ABC = 180°
130° +
ABC = 180°
ABC = 180°-130° = 50°
OBE = 50°
From (i)
CBO =
OBE = 50°
CBE =
CBO +
OBE = 50° + 50° = 100°.