the angle bisectors BD and CE of a triangle ABC are divided by the incentre I in the ratio 3:2 and 2:1 respectively .Then the ratio. in which I divide the angle bisector through A is
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The angle bisectors BD and CE of a triangle ABC are divided by the incentre I in the ratios 3:2 and 2:1 respectively. Then what is the ratio in which I divides the angle bisector through A ?
A
3:1
Your Answer
B
11:4
Correct Answer
C
6:5
D
7:4
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VIDEO EXPLANATION
ANSWER
Incentre divides the angle bisector in a defined ratio of the length of sides of the triangle
IF
AI
=
a
b+c
......(i)
ID
BI
=
b
a+c
=
2
3
⇒2a+2c=3b......(ii)
IB
CI
=
c
a+b
=
1
2
⇒2c=a+b.....(iii)
using (iii) in (ii)
2a+a+b=3b
3a=2b
b=
2
3a
....(iv)
Again 2c=a+b
2c=a+
2
3a
c=
4
5a
.....(v)
using (iv) and (v) in (i)
IF
AI
=
a
2
3a
+
4
5a
=
8
22
=
4
11
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