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(a) The trigonometric expression is \"\".

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Let \"\", \"\" and \"\".

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 \"\", \"\" and \"\".

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\"\"

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\"\"

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\"\"

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Substitute corresponding values in the above expression.

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\"\"

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\"\".

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(b)

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Result in part(a) \"\".

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\"\"

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\"\".

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(a) \"\".

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(b) \"\".