Cho hàm số \({y = \cos \frac{x}{{x + 1}}}\). Tìm
Ta có:
\({y' = {{\left( {\frac{x}{{x + 1}}} \right)}^\prime }.\left( { - \sin \frac{x}{{x + 1}}} \right) = \frac{{\left( {x + 1} \right) - x}}{{{{\left( {x + 1} \right)}^2}}}.\left( { - \sin \frac{x}{{x + 1}}} \right) = - \frac{{\sin \frac{x}{{x + 1}}}}{{{{\left( {x + 1} \right)}^2}}}}\)
Chọn C.
-- Mod Toán 11
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