Given that : $\"\"$ . \ \

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Apply formula : $\"\"$ .

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$\"\"$

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Apply tangent to each side. \ \

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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then $\"\"$ .

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Substitute the value $\"\"$ in equation (1).

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$\"\"$

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Apply formula : $\"\"$ .

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$\"\"$

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Substitute the value $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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So we can\\'t find the value of tan a. \ \

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\