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Determine whether the following relation is an identity: sin(beta - gamma) cos(alpha - delta) + sin(gamma - alpha) cos(beta - delta) + sin(alpha - beta) cos(gamma - delta) = 0.

1. True
2. False
3. Cannot be determined
4. None of these

Correct answer: True

Solution

Applying the product-to-sum formula to every term produces six sine terms that cancel in pairs, leaving 0, so the relation is an identity.

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