$\"\"$

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Derive the Mollweide $\"\"$ s formula:

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Sine rule:

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$\"\"$

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$\"\"$ .

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$\"\"$ .

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Subtract equation $\"\"$ from $\"\"$ .

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$\"\"$

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$\"\"$ .

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Apply formula : $\"\"$ .

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$\"\"$ . $\"\"$

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In a triangle $\"\"$ , $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Mollweide $\"\"$ s formula is $\"\"$ .

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$\"\"$ .