$\"\"$

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The identity is $\"\"$ .

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$\"\"$

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(Apply sum of angles formula $\"\"$ )

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$\"\"$

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(Apply reciprocal identities: $\"\"$ )

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$\"\"$ $\"\"$

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$\"\"$ (Subtract) \ \

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(Apply reciprocal identities: $\"\"$ )

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$\"\"$

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(Apply quotient identities: $\"\"$ )

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$\"\"$ $\"\"$

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$\"\"$ is an identity. \ \