$\"\"$

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The vector is $\"\"$ .

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Rewrite the vector $\"\"$ .

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The magnitude of the vector u is

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$\"\"$

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$\"\"$

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If $\"\"$ and $\"\"$ are the angle between the vector u and unit vectors i, j and k, then

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$\"\"$ and $\"\"$ .

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$\"\"$ and $\"\"$ are the direction cosines of the vector u.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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The direction cosines are $\"\"$ , $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$ .

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The sum of the squares of the direction cosines is 1.

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$\"\"$

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The direction cosines are $\"\"$ , $\"\"$ and $\"\"$ .