【導(dǎo)讀】函數(shù)xxf1)(=在開(kāi)區(qū)間(0,1)內(nèi)是無(wú)上界的.這是因?yàn)?對(duì)于任一M>1,總有1x:1101???,,2121時(shí)當(dāng)及上任意兩點(diǎn)如果對(duì)于區(qū)間xxxxI?有對(duì)于關(guān)于原點(diǎn)對(duì)稱(chēng)設(shè),,DxD??例3證明函數(shù)不是周期函數(shù)。這與周期定義相矛盾,.sin)(不是周期函數(shù)故xxxf?