Proof

(related to Proposition: \(\exp(0)=1\) (Complex Case))

According to the estimate for the remainder term of the exponential complex function, we have \[\exp(x)=\sum_{n=0}^N\frac{x^n}{n! }+r_{N + 1}(x),\] \[|r_{N + 1}(x)|\le 2\frac{|x|^{N+1}}{(N+1)!}\quad\text{for }|x|\le \frac {N+2}2.\] It follows for \(N=0\) that

\[|\exp(x)-1|\le 2|x|\quad\text{for }|x|\le 1.\]

For any convergent complex sequence \((x_n)_{n\in\mathbb N}\) with \(\lim_{n\to\infty} x_n=0\) it follows

\[\lim_{n\to\infty}|\exp(x_n)-1|=0.\] Thus \[\lim_{n\to\infty}\exp(x_n)=1.\]


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References

Bibliography

  1. Forster Otto: "Analysis 1, Differential- und Integralrechnung einer Veränderlichen", Vieweg Studium, 1983