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設(shè)解 ?????????? ?1)(),(1)(,)]([ )(xxxexf x,1)(1 0 時(shí)當(dāng) ?? x,0?x或 ,12)( ???? xx。20 ?? x,0?x或 ,11)( 2 ???? xx。1??x例 3 ,1)(2 0 時(shí)當(dāng) ?? x,0?x或 ,12)( ???? xx。2?x,0?x或 ,11)( 2 ???? xx。01 ??? x綜上所述 .2,120011,2,)]([2122????????????????????xxxxxexexfxx?6. 基本初等函數(shù) (1) 冪函數(shù) )( 是常數(shù)?? ?xyo xy)1,1(11 2xy ?xy?xy1?xy ?(2) 指數(shù)函數(shù) )1,0( ??? aaay xxay ?xay )1(?)1( ?a)1,0(?xey ?(3) 對(duì)數(shù)函數(shù) )1,0(l o g ??? aaxy axy ln?xy al o g?xya1l o g?)1( ?a)0,1(?自然對(duì)數(shù)函數(shù) (4) 三角函數(shù) 正弦函數(shù) xy sin?xy s in?xy cos?xy co s?余弦函數(shù) 正切函數(shù) xy ta n?xy tan?xy c o t?余切函數(shù) xy co t?(5) 反三角函數(shù) xy a r c si n?xy a r c s i n?反正弦函數(shù)xy a r c c o s?xy a r c c o s?反余弦函數(shù)xy a r ct a n?xy a r c ta n?反正切函數(shù) 冪函數(shù) ,指數(shù)函數(shù) ,對(duì)數(shù)函數(shù) ,三角函數(shù)和反三角函數(shù)統(tǒng)稱(chēng)為 基本初等函數(shù) . xy c o t?反余切函數(shù) arcxy co t?arc 由常數(shù)和基本初等函數(shù)經(jīng)過(guò)有限次四則運(yùn)算和有限次的函數(shù)復(fù)合步驟所構(gòu)成 ,并可用 一個(gè)式子表示的函數(shù) ,稱(chēng)為 初等函數(shù) . 7. 初等函數(shù) 例如 0,0,???????xxxxy 可表為 ,2xy ? 故為初等函數(shù) . 符號(hào)函數(shù) ???????????010001s gnxxxxy當(dāng)當(dāng)當(dāng)為非初等函數(shù) . 8.