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The angle between the two Vectors vec(A)...

The angle between the two Vectors `vec(A)= 3hat(i)+4hat(j)+5hat(k)` and `vec(B)= 3hat(i)+4hat(j)-5hat(k)` will be

A

Zero

B

`45^(@)`

C

`90^(@)`

D

`180^(@)`

Text Solution

Verified by Experts

The correct Answer is:
C
`vec(A)= 3hat(i)+4hat(j)+5hat(k), vec(B)= 3hat(i)+4hat(j)-5hat(k)`
`vec(A).vec(B)= (3hat(i)+4hat(j)+5hat(k)).(3hat(i)+4hat(j)-5hat(k))`
`|vec(A)||vec(B)| cos theta = 9+16-25=0`
`|vec(A)|!=0,|vec(B)|!=0, hence, cos theta=0, theta= 90^(@)`
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Knowledge Check

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