What is the sum of the two power series ∑n=0∞(−1)nx2n(2n)!+∑n=0∞(−1)nx2n+1(2n+1)!\sum_{n=0}^{\infty} \frac{(-1)^n x^{2n}}{(2n)!} + \sum_{n=0}^{\infty} \frac{(-1)^n x^{2n+1}}{(2n+1)!}∑n=0∞(2n)!(−1)nx2n+∑n=0∞(2n+1)!(−1)nx2n+1?
exe^xex
eixe^{ix}eix
sin(x)+cos(x)\sin(x) + \cos(x)sin(x)+cos(x)
tan(x)\tan(x)tan(x)