MathDB

Angle bisector

Source: Canada 1969, Problem 5

May 14, 2006

trigonometryratiogeometryblogssearchangle bisector

Problem Statement

Let

ABC

be a triangle with sides of length

a

b

and

c

. Let the bisector of the angle

C

cut

AB

D

. Prove that the length of

CD

\frac{2ab\cos \frac{C}{2}}{a+b}.