sinx=∑n=0∞(−1)nx2n+1(2n+1)!\sin x = \sum_{n=0}^\infty \frac{(-1)^n x^{2n+1}}{(2n+1)!}sinx=∑n=0∞(2n+1)!(−1)nx2n+1, cosx=∑n=0∞(−1)nx2n(2n)!\cos x = \sum_{n=0}^\infty \frac{(-1)^n x^{2n}}{(2n)!}cosx=∑n=0∞(2n)!(−1)nx2n.