Khai triển Maclaurin của cosx đến x4

\[1 - \frac{{{x^2}}}{2} + \frac{{{x^4}}}{{24}} + o({x^5})\]

\[1 + \frac{{{x^2}}}{2} - \frac{{{x^4}}}{{24}} + o({x^5})\]

\[1 - \frac{{{x^2}}}{2} - \frac{{{x^4}}}{{24}} + o({x^5})\]

\[1 + \frac{{{x^2}}}{2} + \frac{{{x^4}}}{{24}} + o({x^5})\]