Tìm khai triển Maclaurin của \[f\left( x \right) = \sqrt {1 + \sin x} - \cos x\] đến x3?

\[f\left( x \right) = \frac{1}{2}x + \frac{3}{8}{x^2} - \frac{1}{{48}}{x^3} + o\left( {{x^3}} \right)\]

\[f\left( x \right) = \frac{1}{2}x + \frac{3}{8}{x^2} + \frac{1}{{48}}{x^3} + o\left( {{x^3}} \right)\]

\[f\left( x \right) = \frac{1}{2}x - \frac{3}{8}{x^2} - \frac{1}{{48}}{x^3} + o\left( {{x^3}} \right)\]

\[f\left( x \right) = \frac{1}{2}x + \frac{1}{8}{x^2} - \frac{1}{{48}}{x^3} + o\left( {{x^3}} \right)\]