RRB NTPC Mains or Stage 2 Model Paper 8 with solutions

Question : 11 of 120

Marks: +1, -0

In a triangle ABC, the internal bisector of the angle A meets BC at D. If AB = 4, AC = 3 and ÐA = 60° , then the length of AD is

Solution:

(b)

Using the theorem of angle of bisector,

{BD}/{DC}={AB}/{AC}=4/3

⇒BD=4/7X& DC=3/7X

In ΔABD, by sine rule,{sin30}/{4/ 7 x} ={sinB}/Y ...(i)

In ΔABC, by sine rule;{sin 60}/X ={sin B}/3

or√3/{2x}={sin30.y}/{4/ {7x× 3}}

[putting the value of sin B from (i)]

⇒Y=√3/2X×4/7X×3×2/1={12√3}/7

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