$\"\"$

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The function is $\"\"$ .

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$ .Apply the trigonometry function of derivative: $\"\"$ .

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$\"\"$ .

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Newtons method:

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$\"\"$

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$\"\"$ .

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$\"\"$

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$\"\"$

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Find $\"\"$

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$\"\"$

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$\"\"$

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Find $\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$