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    Question

    Evaluate the following: cos 40° × cos 40° +

    sin 40° × sin 40°
    B 1 Correct Answer Incorrect Answer
    C 1/2 Correct Answer Incorrect Answer
    D 1/√2 Correct Answer Incorrect Answer

    Solution

    We know that, cos (a − b) = cos a × cos b + sin a × sin b So, cos 40° × cos 40° + sin 40° × sin 40°
    = cos (40° − 40°)
    = cos 0°
    = 1

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