New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    Simplify: sin 780° sin 480° + cos 120° sin

    30°
    B 2/3 Correct Answer Incorrect Answer
    C 1/3 Correct Answer Incorrect Answer
    D 1/2 Correct Answer Incorrect Answer

    Solution

    sin 780°sin 480° + cos 120° sin 30° sin (360° x 2 + 60° ) sin (360° + 120° ) + cos (90° + 30° ) sin30° sin 60° sin 120° - sin 30° sin 30° = [√ 3/2] sin (90° + 30° ) [1/2] [1/2] - = [√3/2] cos 30° - 1/4 = [√ 3/2] [√ 3/2] - 1/4 = 3/4-1/4 = 2/4 = 1/2

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