The angle between the vectors (i + j + k) and (i- j - k) is

1.	The angle between the vectors (i + j + k) and (i- j - k) is
Answer» `"SIN"^(-1) (sqrt8)/(3)` `cos^(-1) ((2)/(3))` `"cos"^(-1) (sqrt8)/(3)` `sin^(-1) ((8)/(9))` ANSWER :A

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