首页 > 代码库 > 关于$\bf{Riemann-Lebesgue引理}$的专题讨论

关于$\bf{Riemann-Lebesgue引理}$的专题讨论

$\bf命题:(Riemann-Lebesgue引理)$设函数$f\left( x \right)$在$\left[ {a,b} \right]$上可积,则

\mathop {\lim }\limits_{\lambda  \to {\rm{ + }}\infty } \int_a^b {f\left( x \right)\sin \lambda xdx}  = 0

<script id="MathJax-Element-1" type="math/tex; mode=display">\mathop {\lim }\limits_{\lambda \to {\rm{ + }}\infty } \int_a^b {f\left( x \right)\sin \lambda xdx} = 0</script>

参考答案

$\bf命题:(Riemann-Lebesgue引理的推广)$ 设函数$f\left( x \right),g\left( x \right)$均在$\left[ {a,b} \right]$上可积,且$g\left( x \right)$以正数$T$为周期,则\mathop {\lim }\limits_{\lambda  \to {\rm{ + }}\infty } \int_a^b {f\left( x \right)g\left( {\lambda x} \right)dx}  = \frac{1}{T}\int_0^T {g\left( x \right)dx} \int_a^b {f\left( x \right)dx}

<script id="MathJax-Element-2" type="math/tex; mode=display">\mathop {\lim }\limits_{\lambda \to {\rm{ + }}\infty } \int_a^b {f\left( x \right)g\left( {\lambda x} \right)dx} = \frac{1}{T}\int_0^T {g\left( x \right)dx} \int_a^b {f\left( x \right)dx} </script>

参考答案

$\bf命题:$