1.

For any vector a, then the value of (axxhati)^(2)+(a xxhatj)^(2)+(axxhatk)^(2) is

Answer»

`4a^(2)`
`2a^(2)`
`a^(2)`
`3a^(2)`

SOLUTION :Let `a = a_1hati + a_(2) HATJ + a_3hatk`
SINCE, `(a xx hati) . (a xx hati) = |{:(a.a,a.hati),(hati.a,1):}| = |a|^(2) - a_(1)^(2)`
Similarly , `(axxhatj)^(2) =|a|^(2) - a_2^(2)`
and `(a xx hatk)^(2) = |a|^(2) -a_(3)^(2)`
`:. (a xx hati)+ (a xx hatj)^(2) + (a xx hatk)^(2) = 3|a|^(2) - (a_(1)^(2)+ a_(2)^(2) + a_(3)^(2))`
`= 3|a|^(2) - |a|^(2)`
`= 2|a|^(2) = 2a^(2)`


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