in the given figure ,the side BC of triangle ABC has been produced to a point D .If the bisectors of ANGLE ABC and ANGLE ACD meet at point E then prove that ANGLE BEC
=1/2 angle BAC
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Answer:
∠BEC = 1/2∠BAC is proved.
Step-by-step explanation:
Given:-
BE is the bisector of ∠ABC, i.e., ∠ABE = ∠EBC.
Also, CE is the bisector of ∠ACD, i.e., ∠ACE = ∠ECD.
To prove:-
∠BEC = 1/2∠BAC
From the figure,
In ΔBEC,
∠ECD = ∠BEC + ∠EBC (Exterior angle property)
∠BEC = ∠ECD - ∠EBC . . . . . (1)
Similarly,
In ΔABC,
∠ACD = ∠ABC + ∠BAC (Exterior angle property)
∠BAC = ∠ACD - ∠ABC . . . . . (2)
Since CE is the bisector of ∠ACD.
⇒ ∠ACD = ∠ACE + ∠ECD
⇒ ∠ACD = ∠ECD + ∠ECD (As ∠ACE = ∠ECD)
⇒ ∠ACD = 2∠ECD
Also,
BE is the bisector of ∠ABC.
⇒ ∠ABC = ∠ABE + ∠EBC
⇒ ∠ABC = ∠EBC + ∠EBC (As ∠ABE = ∠EBC)
⇒ ∠ABC = 2∠EBC
Substitute the values of ∠ACD and ∠ABC in the equation (2), we get
∠BAC = 2∠ECD - 2∠EBC
∠BAC = 2(∠ECD - ∠EBC) . . . . . (3)
From (1) and (3), we have
∠BAC = 2∠BEC
1/2∠BAC = ∠BEC
Hence proved.
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