Question

O is any point inside triangle ABC the bisector of angle AOB, angle BOC and angle COA meet the sides AB,BC and CA the point D,E and F respectively show that AD*BE*CF=DB*EC*FA

Answer 1

see the picture
use angular bisector theorem.

Answer 2

In ∆ AOB, OD is the bisector of angle AOB

OA/OB =AD/DB---------------eq(1)

 

Theorem used here

[The internal bisector of an angle of a triangle divides the opposite side internally in the ratio of the sides containing the angle]

In ∆BOC .OE is the bisector of angle BOC

OB/OC = BE/EC---------eq(2)

In  ∆COA, OF is the bisector of angle COA

OC/OA =CF/FA-----------eq(3)

Multiplying eq 1, 2, 3 

(OA/OB) * (OB/OC)  * (OC/OA) = (AD/DB) * (BE/EC) * (CF/FA)

1= (AD/DB) * (BE/EC) * (CF/FA)

DB*EC*FA = AD*BE*CF

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AD*BE*CF = DB*EC*FA

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Hope this will help you....