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Evaluate the trigonometric expression sin(420 deg)*cos(390 deg) + cos(-300 deg)*sin(-330 deg).

1. 1
2. 1/2
3. sqrt(3)/2
4. 0

Correct answer: 1

Solution

Reducing the angles gives (sqrt3/2)(sqrt3/2) + (1/2)(1/2) = 3/4 + 1/4 = 1.

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