APFIVE Identifying a Function from a Maclaurin Series
A function $$f$$ has Maclaurin series given by $$\displaystyle 1 + \frac{x^2}{2!} + \frac{x^4}{4!} + \frac{x^6}{6!} + \cdots + \frac{x^{2n}}{(2n)!} + \cdots$$ Which of the following is an expression for $$f(x)$$?
A
$$e^{x^2}$$
B
$$\frac{1}{2}(e^x + e^{-x})$$
C
$$e^x - \sin x$$
D
$$\cos x$$
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