$\"\"$

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Need to prove $\"\"$ .

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Consider $\"\"$ .

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If $\"\"$ , then $\"\"$ .

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$\"\"$

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$\"\"$ .

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The Pythagoras theorem, $\"\"$ .

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$\"\"$

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$\"\"$ .

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Ratio of Sine function: $\"\"$ .

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$\"\"$

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Also $\"\"$ .

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Therefore, $\"\"$ .

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$\"\"$

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$\"\"$ .