Prove that the angle bisector of any angle of a triangle and the perpendicular bisector of the opposite side if intersect, will intersect on the circumcircle of the triangle.
Given: The angle bisector of any angle of a triangle and the perpendicular bisector of the opposite side intersect on the circumcircle of the triangle.
Consider DABC
Let the angle bisector of angle A intersect the circumcircle of triangle ABC at point D.
Join DC and DB
BCD = BAD (Angle in the same segment are equal)
BCD = BAD = A … (1) (AD is bisector of ÐCAB)
Similarly,
DAC = DBC (Angle in the same segment are equal)
DBC =DAC = ÐA … (2) (AD is bisector of ÐCAB)
From (1) and (2) we have
DBC =BCD
BD = DC (sides opposite to equal angles in a triangle are equal)
Hence, D also lies on the perpendicular bisector of BC.
Hence, proved