$\"\"$

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$\"\"$ .

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Consider $\"\"$ .

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Definition of derivative : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Trigonometric properties of limits: $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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$\"\"$ .