新高考數(shù)學(xué)一輪復(fù)習(xí)講義 第41講 橢圓及其性質(zhì)（原卷版）

第41講橢圓及其性質(zhì)（精講）題型目錄一覽①橢圓的定義及其應(yīng)用②求橢圓的標(biāo)準(zhǔn)方程③橢圓的幾何性質(zhì)④橢圓的離心率一、知識(shí)點(diǎn)梳理一、知識(shí)點(diǎn)梳理一、橢圓的定義平面內(nèi)與兩個(gè)定點(diǎn)SKIPIF1<0的距離之和等于常數(shù)SKIPIF1<0（SKIPIF1<0）的點(diǎn)的軌跡叫做橢圓，這兩個(gè)定點(diǎn)叫做橢圓的焦點(diǎn)，兩焦點(diǎn)的距離叫做橢圓的焦距，記作SKIPIF1<0，定義用集合語(yǔ)言表示為：SKIPIF1<0注意：當(dāng)SKIPIF1<0時(shí)，點(diǎn)的軌跡是線段；當(dāng)SKIPIF1<0時(shí)，點(diǎn)的軌跡不存在．二、橢圓的方程、圖形與性質(zhì)焦點(diǎn)的位置焦點(diǎn)在SKIPIF1<0軸上焦點(diǎn)在SKIPIF1<0軸上圖形標(biāo)準(zhǔn)方程SKIPIF1<0SKIPIF1<0統(tǒng)一方程SKIPIF1<0參數(shù)方程SKIPIF1<0SKIPIF1<0第一定義到兩定點(diǎn)SKIPIF1<0的距離之和等于常數(shù)2SKIPIF1<0，即SKIPIF1<0（SKIPIF1<0）范圍SKIPIF1<0且SKIPIF1<0SKIPIF1<0且SKIPIF1<0頂點(diǎn)SKIPIF1<0、SKIPIF1<0SKIPIF1<0、SKIPIF1<0SKIPIF1<0、SKIPIF1<0SKIPIF1<0、SKIPIF1<0軸長(zhǎng)長(zhǎng)軸長(zhǎng)SKIPIF1<0，短軸長(zhǎng)SKIPIF1<0長(zhǎng)軸長(zhǎng)SKIPIF1<0，短軸長(zhǎng)SKIPIF1<0對(duì)稱性關(guān)于SKIPIF1<0軸、SKIPIF1<0軸對(duì)稱，關(guān)于原點(diǎn)中心對(duì)稱焦點(diǎn)SKIPIF1<0、SKIPIF1<0SKIPIF1<0、SKIPIF1<0焦距SKIPIF1<0SKIPIF1<0離心率SKIPIF1<0對(duì)于過(guò)橢圓上一點(diǎn)SKIPIF1<0的切線方程，只需將橢圓方程中SKIPIF1<0換為SKIPIF1<0，SKIPIF1<0換為SKIPIF1<0可得焦半徑最大值SKIPIF1<0，最小值SKIPIF1<0【常用結(jié)論】1.過(guò)橢圓的焦點(diǎn)與橢圓的長(zhǎng)軸垂直的直線被橢圓所截得的線段稱為橢圓的通徑，其長(zhǎng)為SKIPIF1<0．①橢圓上到中心距離最小的點(diǎn)是短軸的兩個(gè)端點(diǎn)，到中心距離最大的點(diǎn)是長(zhǎng)軸的兩個(gè)端點(diǎn)．②橢圓上到焦點(diǎn)距離最大和最小的點(diǎn)是長(zhǎng)軸的兩個(gè)端點(diǎn)．距離的最大值為SKIPIF1<0，距離的最小值為SKIPIF1<0．2.橢圓的切線①橢圓SKIPIF1<0上一點(diǎn)SKIPIF1<0處的切線方程是SKIPIF1<0；②過(guò)橢圓SKIPIF1<0外一點(diǎn)SKIPIF1<0，所引兩條切線的切點(diǎn)弦方程是SKIPIF1<0；③橢圓SKIPIF1<0與直線SKIPIF1<0相切的條件是SKIPIF1<0．二、題型分類精講二、題型分類精講題型一橢圓的定義及其應(yīng)用策略方法橢圓定義的應(yīng)用類型及方法(1)探求軌跡：確認(rèn)平面內(nèi)與兩定點(diǎn)有關(guān)的軌跡是不是橢圓．(2)應(yīng)用定義轉(zhuǎn)化：涉及焦半徑的問(wèn)題，常利用|PF1|＋|PF2|＝2a實(shí)現(xiàn)等量轉(zhuǎn)換．(3)焦點(diǎn)三角形問(wèn)題：常把正、余弦定理同橢圓定義相結(jié)合，求焦點(diǎn)、三角形的面積等問(wèn)題．【典例1】（單選題）橢圓SKIPIF1<0的兩個(gè)焦點(diǎn)分別為SKIPIF1<0，過(guò)SKIPIF1<0的直線交橢圓于A、B兩點(diǎn)，則SKIPIF1<0的周長(zhǎng)是（

）A．10 B．12 C．16 D．20【題型訓(xùn)練】一、單選題1．方程SKIPIF1<0的化簡(jiǎn)結(jié)果是（）A．SKIPIF1<0 B．SKIPIF1<0C．SKIPIF1<0 D．SKIPIF1<02．已知點(diǎn)P為橢圓SKIPIF1<0上的一點(diǎn)，SKIPIF1<0，SKIPIF1<0為該橢圓的兩個(gè)焦點(diǎn)，若SKIPIF1<0，則SKIPIF1<0（

）A．SKIPIF1<0 B．SKIPIF1<0 C．1 D．33．橢圓SKIPIF1<0的兩個(gè)焦點(diǎn)分別為SKIPIF1<0，過(guò)SKIPIF1<0的直線交橢圓于A、B兩點(diǎn)，則SKIPIF1<0的周長(zhǎng)是（

）A．10 B．12 C．16 D．204．已知橢圓SKIPIF1<0為兩個(gè)焦點(diǎn)，SKIPIF1<0為橢圓SKIPIF1<0上一點(diǎn)，若SKIPIF1<0的周長(zhǎng)為4，則SKIPIF1<0（

）A．2 B．3 C．SKIPIF1<0 D．SKIPIF1<05．已知SKIPIF1<0是橢圓SKIPIF1<0的兩個(gè)焦點(diǎn)，點(diǎn)M在C上，則SKIPIF1<0的最大值為（

）A．8 B．9 C．16 D．186．已知SKIPIF1<0的頂點(diǎn)SKIPIF1<0在橢圓SKIPIF1<0上，頂點(diǎn)SKIPIF1<0是橢圓的一個(gè)焦點(diǎn)，且橢圓的另外一個(gè)焦點(diǎn)在SKIPIF1<0邊上，則SKIPIF1<0的周長(zhǎng)是（

）A．12 B．SKIPIF1<0 C．16 D．107．已知橢圓SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，點(diǎn)P是橢圓C上的動(dòng)點(diǎn)，SKIPIF1<0，SKIPIF1<0，則SKIPIF1<0的最小值為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<08．已知橢圓C：SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，A是C上一點(diǎn)，SKIPIF1<0，則SKIPIF1<0的最大值為（

）A．7 B．8 C．9 D．119．已知SKIPIF1<0是橢圓SKIPIF1<0的左焦點(diǎn)，點(diǎn)SKIPIF1<0在SKIPIF1<0上，SKIPIF1<0在SKIPIF1<0上，則SKIPIF1<0的最大值是（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<0二、填空題10．若SKIPIF1<0，SKIPIF1<0，點(diǎn)P到SKIPIF1<0，SKIPIF1<0的距離之和為10，則點(diǎn)P的軌跡方程是11．已知橢圓SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，過(guò)SKIPIF1<0的直線交橢圓于A，B兩點(diǎn)，若SKIPIF1<0，則SKIPIF1<0.12．已知橢圓SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0、SKIPIF1<0，若橢圓上的點(diǎn)SKIPIF1<0滿足SKIPIF1<0，則SKIPIF1<013．已知橢圓SKIPIF1<0的左、右焦點(diǎn)分別為F1，F(xiàn)2，點(diǎn)P在橢圓上，若線段PF1的中點(diǎn)在y軸上，|PF1|－|PF2|＝.14．設(shè)SKIPIF1<0是橢圓SKIPIF1<0的左焦點(diǎn)，P為橢圓上任一點(diǎn)，點(diǎn)Q的坐標(biāo)為SKIPIF1<0，則SKIPIF1<0的最大值為.題型二求橢圓的標(biāo)準(zhǔn)方程策略方法待定系數(shù)法求橢圓標(biāo)準(zhǔn)方程的一般步驟【典例1】寫(xiě)出適合下列條件的橢圓的標(biāo)準(zhǔn)方程：（1）兩個(gè)焦點(diǎn)在坐標(biāo)軸上，且經(jīng)過(guò)A(SKIPIF1<0，－2)和B(－2SKIPIF1<0，1)兩點(diǎn)；（2）a＝4，c＝SKIPIF1<0；（3）過(guò)點(diǎn)P(－3，2)，且與橢圓SKIPIF1<0有相同的焦點(diǎn)．【題型訓(xùn)練】一、單選題1．“SKIPIF1<0”是“方程SKIPIF1<0表示橢圓”的（

）A．充分不必要條件 B．必要不充分條件C．充要條件 D．既不充分也不必要條件2．設(shè)橢圓SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0，上頂點(diǎn)為B．若SKIPIF1<0，則該橢圓的方程為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<03．已知橢圓C的中心為坐標(biāo)原點(diǎn)，焦點(diǎn)在y軸上，F(xiàn)1，F(xiàn)2為C的兩個(gè)焦點(diǎn)，C的短軸長(zhǎng)為4，且C上存在一點(diǎn)P，使得｜PF1｜＝6｜PF2｜，則C的方程可能為（）A．SKIPIF1<0＋SKIPIF1<0＝1 B．SKIPIF1<0＋SKIPIF1<0＝1C．SKIPIF1<0＋SKIPIF1<0＝1 D．SKIPIF1<0＋SKIPIF1<0＝14．已知橢圓SKIPIF1<0的左、右焦點(diǎn)分別為SKIPIF1<0，M為C上一點(diǎn)，若SKIPIF1<0的中點(diǎn)為SKIPIF1<0，且SKIPIF1<0的周長(zhǎng)為SKIPIF1<0，則C的標(biāo)準(zhǔn)方程為（

）A．SKIPIF1<0 B．SKIPIF1<0C．SKIPIF1<0 D．SKIPIF1<05．已知橢圓C的焦點(diǎn)為SKIPIF1<0，SKIPIF1<0．過(guò)點(diǎn)SKIPIF1<0的直線與C交于A，B兩點(diǎn)．若SKIPIF1<0的周長(zhǎng)為12，則橢圓C的標(biāo)準(zhǔn)方程為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<06．已知直線SKIPIF1<0經(jīng)過(guò)焦點(diǎn)在坐標(biāo)軸上的橢圓的兩個(gè)頂點(diǎn)，則該橢圓的方程為（

）A．SKIPIF1<0 B．SKIPIF1<0C．SKIPIF1<0 D．SKIPIF1<07．已知橢圓SKIPIF1<0：SKIPIF1<0右焦點(diǎn)為SKIPIF1<0，其上下頂點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，點(diǎn)SKIPIF1<0，SKIPIF1<0，則該橢圓的標(biāo)準(zhǔn)方程為（

）A．SKIPIF1<0 B．SKIPIF1<0C．SKIPIF1<0 D．SKIPIF1<08．若橢圓SKIPIF1<0的中心為坐標(biāo)原點(diǎn)?焦點(diǎn)在SKIPIF1<0軸上；順次連接SKIPIF1<0的兩個(gè)焦點(diǎn)?一個(gè)短軸頂點(diǎn)構(gòu)成等邊三角形，順次連接SKIPIF1<0的四個(gè)頂點(diǎn)構(gòu)成四邊形的面積為SKIPIF1<0，則SKIPIF1<0的方程為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<09．阿基米德（公元前287年—公元前212年）不僅是著名的物理學(xué)家，也是著名的數(shù)學(xué)家，他利用“逼近法”得到橢圓的面積除以圓周率等于橢圓的長(zhǎng)半軸與短半軸的乘積．若橢圓C的對(duì)稱軸為坐標(biāo)軸，焦點(diǎn)在y軸上，且橢圓C的離心率為SKIPIF1<0，面積為SKIPIF1<0，則橢圓C的方程為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<0二、填空題10．已知橢圓C：SKIPIF1<0＋SKIPIF1<0＝1（a＞b＞0），若長(zhǎng)軸長(zhǎng)為6，且兩焦點(diǎn)恰好將長(zhǎng)軸三等分，則此橢圓的標(biāo)準(zhǔn)方程為.11．若橢圓的兩焦點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，點(diǎn)P在橢圓上，且三角形SKIPIF1<0的面積的最大值為12，則此橢圓方程是．12．若一個(gè)橢圓的長(zhǎng)軸長(zhǎng)2a，短軸長(zhǎng)2b，焦距2c成等差數(shù)列，則SKIPIF1<0＝.13．已知SKIPIF1<0，SKIPIF1<0兩點(diǎn)在對(duì)稱軸為坐標(biāo)軸的橢圓上，則橢圓的標(biāo)準(zhǔn)方程為.三、解答題14．根據(jù)下列條件求橢圓的標(biāo)準(zhǔn)方程(1)兩個(gè)焦點(diǎn)的坐標(biāo)分別是SKIPIF1<0、SKIPIF1<0，橢圓上一點(diǎn)P到兩焦點(diǎn)距離的和等于10；(2)兩個(gè)焦點(diǎn)的坐標(biāo)分別是SKIPIF1<0、SKIPIF1<0，并且橢圓經(jīng)過(guò)點(diǎn)SKIPIF1<0；(3)橢圓經(jīng)過(guò)兩點(diǎn)SKIPIF1<0，SKIPIF1<0；(4)離心率為SKIPIF1<0且過(guò)點(diǎn)SKIPIF1<0；題型三橢圓的幾何性質(zhì)策略方法利用橢圓幾何性質(zhì)求值或范圍的思路(1)將所求問(wèn)題用橢圓上點(diǎn)的坐標(biāo)表示，利用坐標(biāo)范圍構(gòu)造函數(shù)或不等關(guān)系．(2)將所求范圍用a，b，c表示，利用a，b，c自身的范圍、關(guān)系求解．【典例1】（單選題）已知SKIPIF1<0、SKIPIF1<0為橢圓SKIPIF1<0的左、右焦點(diǎn)，M為SKIPIF1<0上的點(diǎn)，則SKIPIF1<0面積的最大值為（

）A．SKIPIF1<0 B．2 C．SKIPIF1<0 D．4【題型訓(xùn)練】一、單選題1．橢圓SKIPIF1<0的短半軸長(zhǎng)為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<02．橢圓SKIPIF1<0的焦點(diǎn)坐標(biāo)是（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<03．已知橢圓SKIPIF1<0：SKIPIF1<0的一個(gè)焦點(diǎn)的坐標(biāo)為SKIPIF1<0，則SKIPIF1<0（

）A．1 B．2 C．5 D．94．國(guó)家體育場(chǎng)（又名鳥(niǎo)巢）將再次承辦奧運(yùn)會(huì)開(kāi)幕式．在手工課上，張老師帶領(lǐng)同學(xué)們一起制作了一個(gè)近似鳥(niǎo)巢的金屬模型，其俯視圖可近似看成是兩個(gè)大小不同，扁平程度相同的橢圓，已知大橢圓的長(zhǎng)軸長(zhǎng)為40cm，短軸長(zhǎng)為20cm，小橢圓的短軸長(zhǎng)為10cm，則小橢圓的長(zhǎng)軸長(zhǎng)為（

）cm

A．30 B．10 C．20 D．SKIPIF1<05．已知橢圓SKIPIF1<0的左，右焦點(diǎn)分別為SKIPIF1<0，SKIPIF1<0，SKIPIF1<0，SKIPIF1<0兩點(diǎn)都在SKIPIF1<0上，且SKIPIF1<0，SKIPIF1<0關(guān)于坐標(biāo)原點(diǎn)對(duì)稱，下列說(shuō)法錯(cuò)誤的是（

）A．SKIPIF1<0的最大值為SKIPIF1<0B．SKIPIF1<0為定值C．SKIPIF1<0的焦距是短軸長(zhǎng)的2倍D．存在點(diǎn)SKIPIF1<0，使得SKIPIF1<06．已知SKIPIF1<0是橢圓SKIPIF1<0上一點(diǎn)，SKIPIF1<0、SKIPIF1<0分別是橢圓的左、右焦點(diǎn)，若SKIPIF1<0的周長(zhǎng)為SKIPIF1<0，且橢圓的離心率為SKIPIF1<0，則橢圓上的點(diǎn)到橢圓焦點(diǎn)的最小距離為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<07．已知橢圓SKIPIF1<0的左右焦點(diǎn)分別為SKIPIF1<0，過(guò)SKIPIF1<0的直線交SKIPIF1<0于SKIPIF1<0兩點(diǎn)，直線SKIPIF1<0交SKIPIF1<0軸于點(diǎn)SKIPIF1<0，若SKIPIF1<0，則橢圓SKIPIF1<0的焦距為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<08．點(diǎn)SKIPIF1<0在以SKIPIF1<0為焦點(diǎn)的橢圓SKIPIF1<0上，若線段SKIPIF1<0的中點(diǎn)在SKIPIF1<0軸上，則SKIPIF1<0是SKIPIF1<0的（

）A．3倍 B．4倍 C．5倍 D．7倍二、多選題9．如圖所示，“嫦娥五號(hào)”月球探測(cè)器飛行到月球附近時(shí)，首先在以月球球心F為圓心的圓形軌道Ⅰ上繞月球飛行，然后在P點(diǎn)處變軌進(jìn)入以F為一個(gè)焦點(diǎn)的橢圓軌道Ⅱ繞月球飛行，最后在Q點(diǎn)處變軌進(jìn)入以F為圓心的圓形軌道Ⅲ繞月球飛行，設(shè)圓形軌道Ⅰ的半徑為R，圓形軌道Ⅲ的半徑為r，則（

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A．軌道Ⅱ的長(zhǎng)軸長(zhǎng)為SKIPIF1<0B．軌道Ⅱ的焦距為SKIPIF1<0C．若SKIPIF1<0不變，SKIPIF1<0越小，軌道Ⅱ的短軸長(zhǎng)越大D．若SKIPIF1<0不變，SKIPIF1<0越大，軌道Ⅱ的離心率越小10．如圖所示，用一個(gè)與圓柱底面成θ（SKIPIF1<0）角的平面截圓柱，截面是一個(gè)橢圓．若圓柱的底面圓半徑為2，SKIPIF1<0，則（）A．橢圓的長(zhǎng)軸長(zhǎng)等于4B．橢圓的離心率為SKIPIF1<0C．橢圓的標(biāo)準(zhǔn)方程可以是SKIPIF1<0D．橢圓上的點(diǎn)到一個(gè)焦點(diǎn)的距離的最小值為SKIPIF1<0三、填空題11．已知橢圓SKIPIF1<0的離心率為SKIPIF1<0，則橢圓SKIPIF1<0的長(zhǎng)軸長(zhǎng)為.12．已知橢圓SKIPIF1<0的焦點(diǎn)在x軸上，且長(zhǎng)軸長(zhǎng)是短軸長(zhǎng)的2倍，則SKIPIF1<0．13．設(shè)P是橢圓SKIPIF1<0上任意一點(diǎn)，F(xiàn)為C的右焦點(diǎn)，SKIPIF1<0的最小值為SKIPIF1<0，則橢圓C的長(zhǎng)軸長(zhǎng)為．14．橢圓SKIPIF1<0的內(nèi)接正方形的周長(zhǎng)為．15．橢圓SKIPIF1<0的四個(gè)頂點(diǎn)所圍成的四邊形的面積是.16．已知點(diǎn)(m,n)在橢圓8x2＋3y2＝24上，則m的取值范圍是．17．在手工課上，王老師帶領(lǐng)同學(xué)們一起制作了一個(gè)近似鳥(niǎo)巢的金屬模型，其俯視圖可近似看成是兩個(gè)大小不同、扁平程度相同的橢圓．已知大橢圓的長(zhǎng)軸長(zhǎng)為40cm，短軸長(zhǎng)為20cm，小橢圓的短軸長(zhǎng)為10cm，則小橢圓的長(zhǎng)軸長(zhǎng)為cm.題型四橢圓的離心率策略方法求橢圓離心率或其范圍的方法解題的關(guān)鍵是借助圖形建立關(guān)于a，b，c的關(guān)系式(等式或不等式)，轉(zhuǎn)化為e的關(guān)系式，常用方法如下：(1)直接求出a，c，利用離心率公式e＝eq\f(c,a)求解．(2)由a與b的關(guān)系求離心率，利用變形公式e＝eq\r(1－\f(b2,a2))求解．(3)構(gòu)造a，c的齊次式．離心率e的求解中可以不求出a，c的具體值，而是得出a與c的關(guān)系，從而求得e．【典例1】（單選題）已知橢圓SKIPIF1<0，其上頂點(diǎn)為SKIPIF1<0，左?右焦點(diǎn)分別為SKIPIF1<0，且三角形SKIPIF1<0為等邊三角形，則橢圓SKIPIF1<0的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<0【題型訓(xùn)練】一、單選題1．已知橢圓SKIPIF1<0經(jīng)過(guò)點(diǎn)SKIPIF1<0，則橢圓SKIPIF1<0的離心率為（）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<02．已知橢圓SKIPIF1<0的離心率為SKIPIF1<0，則（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<03．直線l經(jīng)過(guò)橢圓的兩個(gè)頂點(diǎn)，若橢圓中心到l的距離為其長(zhǎng)軸長(zhǎng)的SKIPIF1<0，則該橢圓的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<04．已知橢圓SKIPIF1<0的焦點(diǎn)在SKIPIF1<0軸上，若焦距為4，則該橢圓的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<05．已知SKIPIF1<0是橢圓SKIPIF1<0的左焦點(diǎn)，若過(guò)SKIPIF1<0的直線SKIPIF1<0與圓SKIPIF1<0相切，且SKIPIF1<0的傾斜角為SKIPIF1<0，則橢圓的離心率是（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<06．已知橢圓SKIPIF1<0的上頂點(diǎn)、右頂點(diǎn)、左焦點(diǎn)恰好是等腰三角形的三個(gè)頂點(diǎn)，則橢圓的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<07．已知橢圓SKIPIF1<0為橢圓的對(duì)稱中心，SKIPIF1<0為橢圓的一個(gè)焦點(diǎn)，SKIPIF1<0為橢圓上一點(diǎn)，SKIPIF1<0軸，SKIPIF1<0與橢圓的另一個(gè)交點(diǎn)為點(diǎn)SKIPIF1<0為等腰直角三角形，則橢圓的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<08．已知橢圓SKIPIF1<0的左右焦點(diǎn)分別是SKIPIF1<0，過(guò)SKIPIF1<0的直線交橢圓于SKIPIF1<0兩點(diǎn)，若SKIPIF1<0（SKIPIF1<0為坐標(biāo)原點(diǎn)），SKIPIF1<0，則橢圓SKIPIF1<0的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<09．已知橢圓C：SKIPIF1<0的左右焦點(diǎn)為SKIPIF1<0，過(guò)SKIPIF1<0的直線與SKIPIF1<0交于SKIPIF1<0兩點(diǎn)，若滿足SKIPIF1<0成等差數(shù)列，且SKIPIF1<0，則C的離心率為（

）A．SKIPIF1<0 B．SKIPIF1<0 C．SKIPIF1<0 D．SKIPIF1<010．已知右焦點(diǎn)為SKIPIF1<0的橢圓SKIPIF1<0：SKIPIF1<0上的三點(diǎn)SKIPIF1<0，SKIPIF1<0，SKIPIF