Cho hàm số \(% MathType!MTEF!2!1!+-
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y = \frac{{1 + \sin x}}{{1 + \cos x}}\). Xét hai kết quả:
\(% MathType!MTEF!2!1!+-
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(I) y' = \frac{{\left( {\cos x - \sin x} \right)\left( {1 + \cos x + \sin x} \right)}}{{{{\left( {1 + \cos x} \right)}^2}}}\)
\(% MathType!MTEF!2!1!+-
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(II)y' = \frac{{1 + \cos x + \sin x}}{{{{\left( {1 + \cos x} \right)}^2}}}\)
Kết quả nào đúng ?