$\"\"$

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The intensity is $\"\"$ .

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Consider $\"\"$ .

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Apply reciprocal identities : $\"\"$ and $\"\"$ .

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$\"\"$

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Apply quotient identity : $\"\"$ .

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$\"\"$

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$\"\"$

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Apply pythagorean identity : $\"\"$ .

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$\"\"$

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Therefore, $\"\"$ . $\"\"$

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$\"\"$ .