$$\lim_{x\to0^+}\frac{x^2}{e^{-\frac{1}{x^2}}\cos(\frac{1}{x^2})^2}$$
My intuition is that the denominator goes to 0 faster and everything is non-negative, so the limit is positive infinity.
I cant think of elementary proof, l'Hopital doesn't help here, and I'm not sure if and how to use taylor.
WolframAlpha says it's complex infinity, but I can't understand why it doesn't just real positive infinity.
I've tried to use wolfram language to use the assumption that x is real, but couldn't get any result.
Best Answer
The limit$$\lim_{x\to0^+}\frac{x^2}{\exp\left(-\frac1{x^2}\right)}$$is indeed $+\infty$. Since $\dfrac1{\cos^2\left(\frac1{x^2}\right)}\geqslant1$ for each $x$ (when it is defined), you are right: the limit is $+\infty$.