Find the unit vector vec(b) if −hat(i)+hat(j)−hat(k) bisects the angle between vec(b) and vec(a) =3 hat(i)+4 hat(j)

moiraudjpdn

moiraudjpdn

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2022-08-19

Find the unit vector b if i ^ + j ^ k ^ bisects the angle between b and a = 3 i ^ + 4 j ^
The unit vector along the angle bisector is
i ^ + j ^ k ^ 3 = b + ( 3 5 i ^ + 4 5 j ^ ) | b + 3 5 i ^ + 4 5 j ^ |
Im not able to extract b from here

Answer & Explanation

trazonombresrg

trazonombresrg

Beginner2022-08-20Added 8 answers

You are correct that if   b   is a unit vector and i ^ + j ^ k ^ is angle bisector of b and a   ( = 3 i ^ + 4 j ^ ), we have
i ^ + j ^ k ^ 3 = b + ( 3 5 i ^ + 4 5 j ^ ) | b + 3 5 i ^ + 4 5 j ^ |
Let's say | b + 3 5 i ^ + 4 5 j ^ | = m where m is magnitude.
Then, b =   ( m 3 3 5 ) i ^ + ( m 3 4 5 ) j ^ m 3 k ^   .... ( i )
and ( m 3 3 5 ) 2 + ( m 3 4 5 ) 2 + m 2 3 = 1
Simplifying, m 2 2 m 5 3 = 0
and we get m = 2 5 3
Substituting m in (i),   b = 1 15 ( 11 i ^ + 10 j ^ + 2 k ^ )

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