Question
In parallelogram ABCD, the angle bisector of ∠A bisects BC. Will angle bisector of B also bisect AD? Give reason.
In parallelogram ABCD, the angle bisector of ∠A bisects BC. Will angle bisector of B also bisect AD? Give reason.
Answer:
:
Given, ABCD is a parallelogram, bisector of ∠A, bisects BC at F, i.e. ∠1=∠2, CF = FB.
Draw FE∥BA
ABFE is a parallelogram by construction [∵FE∥BA]
⇒∠1=∠6 [alternate angle]
But ∠1=∠2 [given]
∴∠2=∠6
AB = FB [opposite sides to equal angles are equal] ..... (i)
∴ABFEisarhombus.
Now, in ΔABO and ΔBOF, AB = BF [from Eq. (i)]
BO = BO [common]
AO = FO [diagonals of rhombus bisect each other]
∴ΔABO≅ΔBOF [by SSS]
∠3=∠4 [by CPCT]
Now, BF=12BC [given]
⇒BF=12AD [BC = AD]
⇒AE=12AD [BF = AE]
∴ E is the mid-point of AD.
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:
Given, ABCD is a parallelogram, bisector of ∠A, bisects BC at F, i.e. ∠1=∠2, CF = FB.
Draw FE∥BA
ABFE is a parallelogram by construction [∵FE∥BA]
⇒∠1=∠6 [alternate angle]
But ∠1=∠2 [given]
∴∠2=∠6
AB = FB [opposite sides to equal angles are equal] ..... (i)
∴ABFEisarhombus.
Now, in ΔABO and ΔBOF, AB = BF [from Eq. (i)]
BO = BO [common]
AO = FO [diagonals of rhombus bisect each other]
∴ΔABO≅ΔBOF [by SSS]
∠3=∠4 [by CPCT]
Now, BF=12BC [given]
⇒BF=12AD [BC = AD]
⇒AE=12AD [BF = AE]
∴ E is the mid-point of AD.
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