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    Question

    Simplify (cos20°+sin 20°)

    /(cos20°-sin20°)
    A tan (25°) Correct Answer Incorrect Answer
    B tan (65°) Correct Answer Incorrect Answer
    C cot (65°) Correct Answer Incorrect Answer
    D cot (25°) Correct Answer Incorrect Answer

    Solution

    (cos 20°+sin 20°) / (cos 20°-sin 20°) [(cos 20°+sin 20°)/cos 20°] / [(cos 20°-sin 20°)/cos 20°] = (1+tan 20°)/ (1-tan 20°)       Put tan 45° in place of 1. = (tan45°+tan 20°)/(1-tan 20°×tan 45°) Using the tangent addition formula:   tan(a+b) =(tanA+tanB)/ (1-tanA.tanB) =tan (45°+20°) =tan (65°)

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