x→0lim(tan(4π+x))1/x(1)∞form
={e}^{\underset{x\rightarrow 0}{\mathrm{lim}}\frac{(\mathrm{tan}(\frac{\pi }{4}+x)-1)}{x}}(\underset{x\rightarrow a}{\mathrm{lim}}{(f(x))}^{g(x)}={e}^{(\underset{x\rightarrow a}{\mathrm{lim}}g(x)(f(x)-1))},\underset{x\rightarrow a}{\mathrm{lim}}f(x)=1&\underset{x\rightarrow a}{\mathrm{lim}}g(x)=\infty )
=ex→0limx(1−tanx1+tanx−1)
=ex→0limx(1−tanx)2tanx
=ex→0lim(xtanx)(1−tanx2)
=e(1)(1−02)=e2