# Math Help - how did u calculate this integral

1. ## how did u calculate this integral

wait. my question has been changed:

Use the Riemann-Lebesgue Lemma to get the asymptotic expansion of :

$I(m)=\int_{a}^{\infty}{f(t)cos(mt)dt} \ \ \ \ as \ \ \ \ m\rightarrow\infty$

2. Originally Posted by pengchao1024
$\int_{-\infty}^{\infty}{e^{-x\sqrt{3} r^{2}}dr} \ \ \ \ \ \ \ \ as \ \ \ \ r\rightarrow\infty$
Is it meant to be $\int_{-\infty}^{\infty}{e^{-x\sqrt{3} r^{2}}d{\color{red}x}} \ \ \ \ \ \ \ \ as \ \ \ \ r\rightarrow\infty$ ?