$\"\"$

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(a)

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The trigonometric expression is $\"\"$ .

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Consider $\"\"$ .

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Apply formula : $\"\"$ .

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$\"\"$ .

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The solution is $\"\"$ .

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$\"\"$

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(b)

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The trigonometric expression is $\"\"$ .

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Consider $\"\"$ .

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Apply formula : $\"\"$ .

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$\"\"$

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Apply Pythagorean identity : $\"\"$ .

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$\"\"$ .

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$\"\"$

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(a) The solution is $\"\"$ .

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(b) The solution is $\"\"$ .