《對(duì)數(shù)與對(duì)數(shù)函數(shù)》指數(shù)函數(shù)、對(duì)數(shù)函數(shù)與冪函數(shù)PPT課件(對(duì)數(shù)函數(shù)的性質(zhì)與圖像)
第一部分內(nèi)容:學(xué)習(xí)目標(biāo)
理解對(duì)數(shù)函數(shù)的概念,會(huì)判斷對(duì)數(shù)函數(shù)
初步掌握對(duì)數(shù)函數(shù)的圖像與性質(zhì)
能利用對(duì)數(shù)函數(shù)的性質(zhì)解決與之有關(guān)的問(wèn)題
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對(duì)數(shù)與對(duì)數(shù)函數(shù)PPT,第二部分內(nèi)容:自主學(xué)習(xí)
問(wèn)題導(dǎo)學(xué)
預(yù)習(xí)教材P24-P27的內(nèi)容,思考以下問(wèn)題:
1.對(duì)數(shù)函數(shù)的概念是什么?它的解析式具有什么特點(diǎn)?
2.對(duì)數(shù)函數(shù)的圖像是什么,通過(guò)圖像可觀察到對(duì)數(shù)函數(shù)具有哪些性質(zhì)?
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對(duì)數(shù)與對(duì)數(shù)函數(shù)PPT,第三部分內(nèi)容:新知初探
對(duì)數(shù)函數(shù)
一般地,函數(shù)____________稱為對(duì)數(shù)函數(shù),其中a是常數(shù),a>0且a≠1.
對(duì)數(shù)函數(shù)y=logax的性質(zhì):
(1)定義域是____________,因此函數(shù)圖像一定在y軸的______.
(2)值域是實(shí)數(shù)集______.
(3)函數(shù)圖像一定過(guò)點(diǎn)___________.
(4)當(dāng)a>1時(shí),y=logax是_________;當(dāng)0<a<1時(shí),y=logax是_________.
(5)對(duì)數(shù)函數(shù)的圖像
名師點(diǎn)撥
底數(shù)a與1的大小關(guān)系決定了對(duì)數(shù)函數(shù)圖像的“升降”:當(dāng)a>1時(shí),對(duì)數(shù)函數(shù)的圖像“上升”;當(dāng)0<a<1時(shí),對(duì)數(shù)函數(shù)的圖像“下降”.
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對(duì)數(shù)與對(duì)數(shù)函數(shù)PPT,第四部分內(nèi)容:自我檢測(cè)
1.判斷正誤(正確的打“√”,錯(cuò)誤的打“×”)
(1)函數(shù)y=logx12是對(duì)數(shù)函數(shù).( )
(2)函數(shù)y=2log3x是對(duì)數(shù)函數(shù).( )
(3)函數(shù)y=log3(x+1)的定義域是(0,+∞).( )
2. 函數(shù)f(x)=x-1+lg x的定義域是( )
A.(0,+∞) B.(0,1)
C.[1,+∞) D.(1,+∞)
3. 下列不等號(hào)連接錯(cuò)誤的一組是( )
A.log0.52.2>log0.52.3 B.log34>log65
C.log34>log56 D.logπe>logeπ
4. 函數(shù)y=log(3a-1)x是(0,+∞)上的減函數(shù),則實(shí)數(shù)a的取值范圍是________.
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對(duì)數(shù)與對(duì)數(shù)函數(shù)PPT,第五部分內(nèi)容:講練互動(dòng)
對(duì)數(shù)函數(shù)的概念
例1 判斷下列函數(shù)哪些是對(duì)數(shù)函數(shù)?
(1)y=3log2x;(2)y=log6x;(3)y=logx3;(4)y=log2x+1.
【解】(1)log2x的系數(shù)是3,不是1,不是對(duì)數(shù)函數(shù).
(2)符合對(duì)數(shù)函數(shù)的結(jié)構(gòu)形式,是對(duì)數(shù)函數(shù).
(3)自變量在底數(shù)位置上,不是對(duì)數(shù)函數(shù).
(4)對(duì)數(shù)式log2x后又加1,不是對(duì)數(shù)函數(shù).
規(guī)律方法
判斷一個(gè)函數(shù)是對(duì)數(shù)函數(shù)必須是形如y=logax(a>0且a≠1)的形式,即必須滿足以下條件:
(1)系數(shù)為1.
(2)底數(shù)為大于0且不等于1的常數(shù).
(3)對(duì)數(shù)的真數(shù)僅有自變量x.
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對(duì)數(shù)與對(duì)數(shù)函數(shù)PPT,第六部分內(nèi)容:達(dá)標(biāo)反饋
1.下列函數(shù)是對(duì)數(shù)函數(shù)的是( )
A.y=loga(2x) B.y=log22x
C.y=log2x+1 D.y=lg x
2.函數(shù)f(x)=11-x+lg(3x+1)的定義域是( )
A.-13,+∞ B.-∞,-13
C.-13,13 D.-13,1
3.函數(shù)y=ax與y=-logax(a>0,且a≠1)在同一坐標(biāo)系中的圖像形狀可能是( )
4.若a>0且a≠1,則函數(shù)y=loga(x-1)+1的圖像過(guò)定點(diǎn)為________.
5.比較下列各組數(shù)的大。
(1)log22________log23;
(2)log32________1;
(3)log134________0.
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