1.

If vec A =2 hat i+ 3 hat j+ 8 hat k is perpendicular to vec B= 4 hat j -4 hat i+ alpha hat k, then the value of alpha

Answer»

`(1)/(2)`
`-(1)/(2)`
1
`-1`

SOLUTION :Given :
`A=2HAT(i)+3hat(J)+8hat(k)`
`B=4hat(j)-4hat(i)+alpha HAT(k)`
`=-4hat(i)+4hat(j)+alpha hat(k)`
`A _|_ B` Hence, A. B = 0
`rArr (2hat(i)+3hat(j)+8hat(k))(-4hat(i)+4hat(j)+alpha hat(k))=0`
`rArr -8+12+8alpha=0`
`rArr 8alpha + 4=0`
`rArr 8alpha =-4`
`alpha =-(4)/(8)=-(1)/(2)`


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