Question

28. The angle between the vectors (2î – 39 + 4Â ) and ( 6î - 99 +12Â ) is A) zero B) π/2 rad c) π/3 rad D) π/4 rad ​

Answer 1

Answer:

=2

i

^

+3

j

^

−4

k

^

And

B

=5

i

^

+2

j

^

+4

k

^

Now, as we know

A

.

B

=ABcosθ

θ is the angle between

A

and

B

Therefore,

cosθ=

AB

A

.

B

cosθ=

2

2

+3

2

+(−4)

2

5

2

+2

2

+4

2

(2

i

^

+3

j

^

−4

k

^

).(5

i

^

+2

j

^

+4

k

^

)

=

2

2

+3

2

+(−4)

2

5

2

+2

2

+4

2

(10+6−16)

=0

Therefore, cosθ=0

θ=90

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