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If vec A and vec B ar perpendicular vect...

If `vec A and vec B` ar perpendicular vectors and vector `vec A = 5 hati + 7 hatj - 3 hatk and vec B = 2 hati + 2 hatj - a hatk.` The value of a is

A

`-2 `

B

8

C

`-7`

D

`-8.`

Text Solution

Verified by Experts

The correct Answer is:
D
`vec A . vec B = 0 implies ( 5hati + 7 hatj - 3 hatk ) . (2 hat i + 2 hatj + a hatk ) = 0`
`0 + 14 + 3 a = 0 implies a =- 8.`
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