$\"\"$

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The points are $\"\"$ and $\"\"$ .

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The dot product of $\"\"$ and $\"\"$ is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in the above equation.

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$\"\"$

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$\"\"$

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Thus, $\"\"$ and $\"\"$ are not orthogonal.

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$\"\"$

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$\"\"$ and $\"\"$ are not orthogonal.