小张的小站 - 悬赏 https://www.zhangzujin.cn/forum.php?mod=forumdisplay&fid=96 Latest 20 threads of 悬赏 Copyright(C) 小张的小站 Discuz! Board by Comsenz Inc. Wed, 06 May 2026 23:16:02 +0000 60 https://www.zhangzujin.cn/static/image/common/logo_88_31.gif 小张的小站 https://www.zhangzujin.cn/ 设 $f(x)\\in R[0,1], F(x)=\\int_0^x f(t)\\mathrm{ d} t, DF(x)=\\varlimsup_{h\\to 0}\\frac{F(x+h)-F(x)}{h}$. 求证: $$\\begin{aligned} DF(x)\\in R[0,1]\\mbox{且} \\int_0^1 DF(x)\\mathrm{ d} x=\\int_0^1 f(x)\\mathrm{ d} x. \\end{aligned}$$ https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2305 悬赏 zhangzujin Mon, 05 Jun 2023 00:20:15 +0000 求 $ f(x)=\\frac{1-r^2}{1-2r\\cos x+r^2}\\ (|r|\\lt 1)$ 的 Fourier 级数. https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2304 悬赏 zhangzujin Mon, 05 Jun 2023 00:08:57 +0000 $\\int_a^b xf(x)\\mathrm{ d} x\\leq 0$? https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2292 悬赏 flyy Mon, 22 May 2023 07:37:47 +0000 $\\lim_{n\\to\\infty}\\left\\Vert f_n-f\\right\\Vert _{L^1}=0, \\mbox{且} f_n \\to f$? https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2291 悬赏 flyy Mon, 22 May 2023 06:21:56 +0000 证明: $f(x,y)\\leq \\frac{2}{1-x^2-y^2}, \\forall\\ (x,y)\\in B$. https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2249 悬赏 flyy Fri, 12 May 2023 23:51:16 +0000 $f$ 在 $\\mathbb{R}$ 上连续的充分必要条件 https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2248 悬赏 flyy Fri, 12 May 2023 23:46:24 +0000 $\\lim_{n\\to\\infty}\\sum_{k=1}^n f\\left(\\frac{k}{n^2}\\right)=\\frac{f\'(0)}{2}. $ https://www.zhangzujin.cn/forum.php?mod=viewthread&tid=2247 悬赏 flyy Fri, 12 May 2023 23:41:50 +0000