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In a Delta ABC, if b + c = 3a, then the ...

In a `Delta ABC`, if b + c = 3a, then the value of `cotB/2cotC/2,` is

A

1

B

2

C

`sqrt3`

D

3

Text Solution

Verified by Experts

The correct Answer is:
B
We have,
b+c=3a
`rArrsinB+sinC=3sinA` `[because a/(sinA)=b/(sinB)=c/(sinC)]`
`rArr2sin(B+C)/2cos(B-C)/2=6sinA/2cosA/2`
`rArrcos(B-C)/2=3sinA/2`
`rArr2cosB/2cosC/2=4sinB/2sinC/2rArrcotB/2cotC/2=2`
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