Find limlimits_(n→∞)\[e^(nπ i)-(-1)^n]n+dfrac in\
Find $\ \lim\limits_{n\to\infty}\left\{\left[e^{n\pi i}-(-1)^n\right]n+\dfrac in\right\}$.
Explanation of Method
Recognize $e^{n\pi i}=(-1)^n$ exactly for every integer $n$ (via Euler's formula), which collapses the bracket to zero, leaving only the vanishing term $i/n$.
Step 1 · Simplify $e^{n\pi i}$
$$ e^{n\pi i}=(e^{i\pi})^n=(-1)^n $$
using Euler's identity $e^{i\pi}=-1$.
Step 2 · The bracket vanishes identically
$$ \left[e^{n\pi i}-(-1)^n\right]n=\left[(-1)^n-(-1)^n\right]n=0 $$
for every integer $n$ — not just in the limit.
Step 3 · What remains
$$ \left[e^{n\pi i}-(-1)^n\right]n+\frac in=0+\frac in=\frac in $$
Step 4 · Take the limit
$$ \boxed{\lim_{n\to\infty}\frac in=i\cdot\lim_{n\to\infty}\frac1n=i\cdot0=0} $$
Verification
$\left|\dfrac in\right|=\dfrac1n\to0$, so the sequence's modulus vanishes, confirming convergence to $0$.
Result
The bracket is a disguised identity, not merely a vanishing quantity — recognizing that hidden simplification is the whole problem.