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In triangle ABC, r=(R )/(6) and r(1)=7r....

In triangle `ABC, r=(R )/(6)` and `r_(1)=7r`. Then the measure of angle A =

A

`(pi)/(12)`

B

`(pi)/(6)`

C

`(pi)/(4)`

D

`(pi)/(3)`

Text Solution

Verified by Experts

The correct Answer is:
D
`r_(2)-r_(2)=4R"sin"^(2)(A)/(2)`
Now `r_(1)-r=7r-r=6r=R`
`rArr R=4R"sin"^(2)(A)/(2)`
`rArr A=(pi)/(3)`
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