Pls answer Q. 48.
Need qualitative answer.
Need good explanation.
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If bisectors of interior ∠B and exterior ∠ACD of ΔABC intersect at the point T , then ∠BTC =
(1) 2∠BAC
(2) ½∠BAC
(3) ½∠ABC
(4) 2∠ABC
Solution:
Given:
∆ABC, produce BC to D and the bisectors of ∠ABC and ∠ACD meet at point T.
To Prove:
∠BTC = ½∠BAC
Proof:
∆ABC, ∠ACD is an exterior angle.
∴ ∠ACD = ∠ABC + ∠CAB
[Exterior angle of a triangle is equal to the sum of two opposite angles]
⇒½∠ACD =½∠CAB + ½∠ABC
[Dividing both sides by 2]
⇒ ∠TCD = ½∠CAB + ½∠ABC
[ ∵ CT is a bisector of ∠ACD ⇒½∠ACD = ∠TCD]
In ∆, BTC
∴ ∠TCD = ∠BTC + ∠CBT
[Exterior angle of a triangle is equal to the sum of two opposite angles]
⇒ ∠TCD = ∠BTC + ½∠ABC . . . (ii)
[ ∵ bisector of∠ABC ⇒ ∠CBT =½∠ABC]
From equations (i) and (ii), we get
½∠CAB + ½∠ABC = ∠BTC + ½∠ABC
⇒ ½∠CAB = ∠BTC
or ½∠BAC = ∠BTC
Hence proved.
(1) 2∠BAC
(2) ½∠BAC
(3) ½∠ABC
(4) 2∠ABC
Solution:
Given:
∆ABC, produce BC to D and the bisectors of ∠ABC and ∠ACD meet at point T.
To Prove:
∠BTC = ½∠BAC
Proof:
∆ABC, ∠ACD is an exterior angle.
∴ ∠ACD = ∠ABC + ∠CAB
[Exterior angle of a triangle is equal to the sum of two opposite angles]
⇒½∠ACD =½∠CAB + ½∠ABC
[Dividing both sides by 2]
⇒ ∠TCD = ½∠CAB + ½∠ABC
[ ∵ CT is a bisector of ∠ACD ⇒½∠ACD = ∠TCD]
In ∆, BTC
∴ ∠TCD = ∠BTC + ∠CBT
[Exterior angle of a triangle is equal to the sum of two opposite angles]
⇒ ∠TCD = ∠BTC + ½∠ABC . . . (ii)
[ ∵ bisector of∠ABC ⇒ ∠CBT =½∠ABC]
From equations (i) and (ii), we get
½∠CAB + ½∠ABC = ∠BTC + ½∠ABC
⇒ ½∠CAB = ∠BTC
or ½∠BAC = ∠BTC
Hence proved.
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rekhasuri31:
Tq so much....
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