最新-最新2018年開放教育自考電子商務(wù)概論小抄

1、第一章一、由Internet及相關(guān)技術(shù)決定的電子商務(wù)的特點。二、由電子商務(wù)系統(tǒng)結(jié)構(gòu)決定的電子商務(wù)的特點。三、由交易過程決定的電子商務(wù)特點四、由電子商務(wù)市場主體決定電子商務(wù)的特點。電子商務(wù)的產(chǎn)生原因：第一、信息網(wǎng)絡(luò)技術(shù)為電子商務(wù)的發(fā)展的物質(zhì)基礎(chǔ)；第二、國際經(jīng)貿(mào)的迅速發(fā)展要求商務(wù)手段和工具上的變革；第三、國際市場的激烈競爭也促進(jìn)了電子商務(wù)的發(fā)展。電子商務(wù)的分類1按照交易主體分類：2按照交易對象分類：3按照使用網(wǎng)絡(luò)類型分類：4按照網(wǎng)絡(luò)接入方式分類：電子商務(wù)對企業(yè)的影響。(1)影響企業(yè)的運作方式。(2)影響企業(yè)的組織結(jié)構(gòu)電子商務(wù)對經(jīng)濟(jì)規(guī)律的影響。(1)邊際收益遞減規(guī)律被邊際收益遞增規(guī)律代替。(2)達(dá)維

2、多定律(3)梅特卡夫定律第二章 電子商務(wù)技術(shù)基礎(chǔ)電子商務(wù)支付技術(shù)安全協(xié)議：一，SSL（握手協(xié)議，消息加密協(xié)議；商家欺詐）；二，SET（常用）。Web2.0的主要技術(shù):RSS（信息聚合技術(shù)）；Trackback（引用功能）；Ajax（與服務(wù)器異步通信）；Tag。（標(biāo)簽，關(guān)鍵詞分類技術(shù)）電子支付工具：電子錢夾（電子信用卡）。電子支票電子現(xiàn)金（電子錢包）安全認(rèn)證技術(shù)：智能卡；數(shù)字簽名（非對稱加密技術(shù)）；數(shù)字憑證；CA認(rèn)證；數(shù)字信封；數(shù)字時間戳。第三章 EDIEDI優(yōu)勢一，降低成本。二，減少錯誤。三，減少庫存。四，改善客戶服務(wù)。傳統(tǒng)EDI的局限性一，環(huán)境問題二，費用問題三，安全問題。EDI信息編碼原則

3、包括：一，唯一性。二，簡明性。三，穩(wěn)定性。四，可擴(kuò)展性。五，易識性。六，自檢能力。由動作流程形成的ECI工作方式：一，生產(chǎn)EDI平面文件；二，翻譯生產(chǎn)EDI標(biāo)準(zhǔn)格式文件；三，通訊；四，EDI文件的接受和處理。由功能模型形成的ECI動作方式：一，點對點PTP方式；二，增值網(wǎng)VAN方式；三，MHS方式；電子商務(wù)是EDI發(fā)展的必然趨勢：一，internet mail；二，標(biāo)準(zhǔn)翻譯；三，web-EDI方式；四，XML/EDI方式。第四章 電子商務(wù)系統(tǒng)(利用信息網(wǎng)絡(luò)技術(shù)全面實現(xiàn)電子交易的商務(wù)系統(tǒng))電子商務(wù)系統(tǒng)由4要素組成：Internet信息要素；電子商務(wù)主體要素；電子商務(wù)服務(wù)商要素（1，接入服務(wù)商；2

4、，服務(wù)提供商 3，內(nèi)容服務(wù)提供商 4 應(yīng)用服務(wù)系統(tǒng)提供商。）；中介組織要素（認(rèn)證中心；支付中心；物流中心）。第五章 電子商務(wù)流程（B2C;B2B;C2C）一，電子商務(wù)的基本流程：交易前的準(zhǔn)備；交易磋商；簽訂合同和辦理手續(xù)；廝履行合同的索賠。企業(yè)業(yè)務(wù)流程四要素及內(nèi)容：一，活動，明確活動的內(nèi)容，要做什么；二，活動的方式，用什么做，工具設(shè)備；三，活動的承擔(dān)者；四，活動的連接方式，鏈接手段、方式應(yīng)充分體現(xiàn)管理、控制功能。電子商務(wù)與企業(yè)流程重組：必然性：一，傳統(tǒng)企業(yè)流程模式的缺陷（分工過細(xì)，組織結(jié)構(gòu)臃腫，企業(yè)員工技能單一）；二，信息技術(shù)對傳統(tǒng)業(yè)務(wù)流程的影響。內(nèi)容：1，組織結(jié)構(gòu)重組（一，柔性化；二，網(wǎng)絡(luò)化

5、；三，扁平化；四，團(tuán)隊化。）2，業(yè)務(wù)鏈重組3，資源重組第六章 電子商務(wù)模式電子商務(wù)模式分類：運營模式；贏利模式（一，利潤點。是指企業(yè)可以獲取利潤的產(chǎn)品和服務(wù)。二，利潤對象。是指企業(yè)提供的商品或服務(wù)的購買者和使用群體。三，利潤源。是指企業(yè)的收入來源。四，利潤屏障。是指企業(yè)為了防止競爭者掠奪本企業(yè)的利潤而采取的防范措施。五，利潤杠桿。是指企業(yè)生產(chǎn)產(chǎn)品或服務(wù)以及吸引顧客購買和使用產(chǎn)品或服務(wù)的一系列業(yè)務(wù)活動）。 B2B模式的細(xì)分 一. 賣方集中模式(集中采購)；二. 買方集中模式(集中銷售)；三. 網(wǎng)上/第三方交易市場模式(最流行)。博客贏利模式有：一，平臺收費；二，營銷收費；三，銷售贏利；四，中介收

6、費；五，服務(wù)收費；六，內(nèi)容收費；七，配件收費。長尾理論：只要存儲和流通的渠道足夠大，需求不旺或者銷量不佳的產(chǎn)品所共同占據(jù)的市場份額可以喝那些少數(shù)熱銷產(chǎn)品所占據(jù)的市場份額相匹敵甚至更大，既眾多小市場匯聚可以與主流大市場相匹敵的市場能量。電子商務(wù)主要盈利模式：一， 廣告模式；二，訂閱模式；三，銷售模式；四，會員制模式；五，5Cs。第七章 電子商務(wù)戰(zhàn)略時間：一，戰(zhàn)略的提出；二，戰(zhàn)略的形成；三，戰(zhàn)略的實施；四，戰(zhàn)略的評估?？臻g：一，戰(zhàn)略目的；二，戰(zhàn)略方針；三，戰(zhàn)略力量；四，戰(zhàn)略措施。電子商務(wù)戰(zhàn)略的分類按主體劃分（政府、組織和企業(yè)）；按行業(yè)劃分；按性質(zhì)劃分（(1) 電子商務(wù)競爭戰(zhàn)略。一，搶占快車道戰(zhàn)略。

7、二，人才風(fēng)險戰(zhàn)略。三，另辟蹊徑戰(zhàn)略。四，隱形進(jìn)攻戰(zhàn)略。(2) 電子商務(wù)合作戰(zhàn)略）制定電子商務(wù)戰(zhàn)略步驟：一，戰(zhàn)略的提出；二，外部環(huán)境分析；三，內(nèi)部環(huán)境分析；四，識別差距；五，戰(zhàn)略的形成。企業(yè)電子商務(wù)戰(zhàn)略目標(biāo)注意問題：一，優(yōu)先考慮電子商務(wù)系統(tǒng)的競爭力目標(biāo)；二，應(yīng)基于全球化經(jīng)濟(jì)考慮系統(tǒng)需求（滿足國際需要目標(biāo)）；三，應(yīng)把支撐企業(yè)運營目標(biāo)作為核心要素之一；四，重視電子商務(wù)系統(tǒng)的價值衡量（利潤增值目標(biāo)）；五，建立責(zé)任控制體系企業(yè)電子商務(wù)戰(zhàn)略框架主要包括下列戰(zhàn)略：電子商務(wù)產(chǎn)品戰(zhàn)略、技術(shù)戰(zhàn)略、市場戰(zhàn)略、物流戰(zhàn)略、人才戰(zhàn)略、安全戰(zhàn)略等。企業(yè)電子商務(wù)戰(zhàn)略步驟：一，基礎(chǔ)階段；二，信息孤島階段；三，企業(yè)內(nèi)部信息化階段

8、；四，電子商務(wù)實施階段。第八章 電子商務(wù)產(chǎn)品電子商務(wù)產(chǎn)品分為三類：一，有形電子產(chǎn)品；二，無形電子產(chǎn)品；三，數(shù)字產(chǎn)品；（，可復(fù)制性；，可比性；，具有公共物品性質(zhì)；，具有“經(jīng)驗產(chǎn)品”性質(zhì)）。電子商務(wù)產(chǎn)品的發(fā)展趨勢：一，越來越注重產(chǎn)品內(nèi)容；二，越來越多的產(chǎn)品數(shù)字化；三，越來越多的產(chǎn)品信息化。新產(chǎn)品創(chuàng)新的流程分為六個階段：一，產(chǎn)品概念；二，產(chǎn)品定義；三，產(chǎn)品設(shè)計;四，樣本研制；五，實驗推廣；六，大規(guī)模促銷。電子商務(wù)時代生產(chǎn)模式的特點：一，創(chuàng)新特征；二，更新快特征；三，知識特征 ；四，文化特征；五，個性化服務(wù)特征.有形產(chǎn)品定制化的好處：一，產(chǎn)品功能更具有針對性；二，生產(chǎn)的預(yù)測更準(zhǔn)確；三，定制生產(chǎn)是保持和

9、消費者聯(lián)系的最好途徑；四，動態(tài)貿(mào)易的出現(xiàn)（讓技術(shù)滿足當(dāng)擁有定制客戶的需求）。服務(wù)供給個性化：一，服務(wù)業(yè)最適合電子商務(wù)；二，EC產(chǎn)品發(fā)展趨勢要求服務(wù)業(yè)的配套發(fā)展；三，EC的發(fā)展促進(jìn)了服務(wù)的創(chuàng)新。電子商務(wù)生產(chǎn)方式對企業(yè)的影響：一，企業(yè)成為“學(xué)習(xí)組織”；二，企業(yè)注重知識網(wǎng)絡(luò)建設(shè)；三，企業(yè)功能社會化；四，企業(yè)管理信息化。ERP對企業(yè)的作用：一，維護(hù)盡可能低的庫存量；二，減少停工待料，時間成本；三，提高質(zhì)量，降低人工成本；四，節(jié)省管理人員，降低管理費用。第九章 電子商務(wù)市場電子商務(wù)市場戰(zhàn)略：1.市場進(jìn)攻戰(zhàn)略;2.經(jīng)營業(yè)務(wù)戰(zhàn)略（一，成本領(lǐng)先戰(zhàn)略 二，差異化戰(zhàn)略 三，集中化戰(zhàn)略。）;3.市場合作戰(zhàn)略;4.市

10、場跟進(jìn)戰(zhàn)略；5.市場補(bǔ)缺戰(zhàn)略。電子商務(wù)定價原則：遵循價值規(guī)律；從實際出發(fā)；服務(wù)于企業(yè)目標(biāo)。電子商務(wù)定價的特點一，全球性影響定價；二，打破了產(chǎn)品價格的不對稱；三，降低了交易價格；四，有利于個性化定價五，有利于消費者間的信息溝通和聯(lián)合購買電子商務(wù)定價策略：免費策略，高位定價策略，低位定價策略，個性化定價策略，動態(tài)定價策略，聯(lián)盟定價策略，捆綁定價策略，版本定價策略，網(wǎng)上拍賣定價策略，折扣定價策略。第十章 網(wǎng)絡(luò)營銷網(wǎng)絡(luò)銷售與傳統(tǒng)營銷的比較：一，網(wǎng)絡(luò)銷售具有傳統(tǒng)銷售所無法比擬的優(yōu)勢。二，網(wǎng)絡(luò)銷售的互動性極強(qiáng)，有助于實現(xiàn)企業(yè)的全程目標(biāo)。三，網(wǎng)絡(luò)消費者個性化趨勢日益突出。四，網(wǎng)絡(luò)營銷使消費者購物過程更加容易

11、和理智。五，網(wǎng)絡(luò)營銷有利于降低企業(yè)成本費用，增強(qiáng)競爭優(yōu)勢。網(wǎng)絡(luò)調(diào)研優(yōu)勢：一，突破時空的限制；二，便捷性、經(jīng)濟(jì)型；三，及時性、客觀性；四，數(shù)據(jù)的可再用性和升值。五，可檢驗性和可控性。網(wǎng)絡(luò)調(diào)研的步驟：一，確定網(wǎng)絡(luò)調(diào)研問題和調(diào)研目標(biāo)；二，確定網(wǎng)絡(luò)調(diào)研對象；三，確定網(wǎng)絡(luò)調(diào)研方法；四，信息收集；五，信息整理和分析；六，提出研究報告網(wǎng)絡(luò)調(diào)研主要方法：一，網(wǎng)絡(luò)問卷法；二，網(wǎng)絡(luò)觀察法；三，專題討論法；四，在線實踐法；五，搜索引擎查找資料；六，訪問網(wǎng)站收集信息；七，利用網(wǎng)絡(luò)數(shù)據(jù)庫信息。博客營銷：一，網(wǎng)絡(luò)營銷費用低。二，有利于企業(yè)與消費者交流溝通。三，有利于提高企業(yè)信譽(yù)度和推廣品牌。四，有利于市場調(diào)查和新產(chǎn)品開發(fā)

12、。第十一章 電子商務(wù)的客戶關(guān)系購買的決策過程：一，認(rèn)知問題；二，搜尋信息；三，信息評價與決策；四，購買行為；五，購買后行為。消費者決策的基本原則：一，最大滿意原則；二，相對滿意原則；三，遺憾最小原則；四，預(yù)期滿意原則?？蛻絷P(guān)系管理要素：一， 面對客戶、接觸客戶（提供盡可能多的客戶服務(wù)接入形式；洞察更深層次的客戶需求；注重向哪些更具潛力的客戶提供服務(wù)；個性化的客戶服務(wù)界面；提供一個讓客戶放心的安全環(huán)境）；二處理客戶問題。第十二章 電子商務(wù)采購優(yōu)勢：一，從根本上改變企業(yè)的傳統(tǒng)采購模式，提高效率；二，降低采購成本；三，擴(kuò)大交易范圍；四，提高整體供應(yīng)鏈的獲利能力；五，實現(xiàn)本地化采購向全球化采購的轉(zhuǎn)變。

13、按采購職能與企業(yè)戰(zhàn)略關(guān)系的劃分的電子商務(wù)采購模式：一，按進(jìn)貨性采購模式；二，單獨業(yè)務(wù)性采購模式；三，戰(zhàn)略職員型采購模式；四，部門統(tǒng)合性采購模式；五，定制采購模式。第十三章 電子商務(wù)物流EC與物流的關(guān)系：一，物流是電子商務(wù)的一部分；二，物流是實現(xiàn)電子商務(wù)的關(guān)鍵；三，電子商務(wù)改變了傳統(tǒng)的物流運作方式，促進(jìn)了物流的發(fā)展。EC物流和傳統(tǒng)物流的關(guān)系：相同：運輸功能存儲功能裝卸搬運功能包裝功能不同：信息化網(wǎng)絡(luò)化現(xiàn)代化社會化柔性化EC物流系統(tǒng)目標(biāo)的設(shè)定：服務(wù)性目標(biāo)快捷目標(biāo)低成本目標(biāo)安全性目標(biāo)EC物流基本技術(shù)：條碼技術(shù)射頻技術(shù)地理信息系統(tǒng)GPS技術(shù)第三方物流優(yōu)勢：集中精力發(fā)展主業(yè)減少庫存量，降低庫存成本減少資

14、本積壓，節(jié)省費用提升企業(yè)形象延伸服務(wù)劣勢：企業(yè)對物流控制能力降低客戶關(guān)系管理風(fēng)險客戶信息透露的危險請您刪除一下內(nèi)容，O(_)O謝謝！2018年中央電大期末復(fù)習(xí)考試小抄大全，電大期末考試必備小抄，電大考試必過小抄Acetylcholine is a neurotransmitter released from nerve endings (terminals) in both the peripheral and the central nervous systems. It is synthesized within the nerve terminal from choline, taken

15、 up from the tissue fluid into the nerve ending by a specialized transport mechanism. The enzyme necessary for this synthesis is formed in the nerve cell body and passes down the axon to its end, carried in the axoplasmic flow, the slow movement of intracellular substance (cytoplasm). Acetylcholine

16、is stored in the nerve terminal, sequestered in small vesicles awaiting release. When a nerve action potential reaches and invades the nerve terminal, a shower of acetylcholine vesicles is released into the junction (synapse) between the nerve terminal and the effector cell which the nerve activates

17、. This may be another nerve cell or a muscle or gland cell. Thus electrical signals are converted to chemical signals, allowing messages to be passed between nerve cells or between nerve cells and non-nerve cells. This process is termed chemical neurotransmission and was first demonstrated, for nerv

18、es to the heart, by the German pharmacologist Loewi in 1921. Chemical transmission involving acetylcholine is known as cholinergic. Acetylcholine acts as a transmitter between motor nerves and the fibres of skeletal muscle at all neuromuscular junctions. At this type of synapse, the nerve terminal i

19、s closely apposed to the cell membrane of a muscle fibre at the so-called motor end plate. On release, acetylcholine acts almost instantly, to cause a sequence of chemical and physical events (starting with depolarization of the motor endplate) which cause contraction of the muscle fibre. This is ex

20、actly what is required for voluntary muscles in which a rapid response to a command is required. The action of acetylcholine is terminated rapidly, in around 10 milliseconds; an enzyme (cholinesterase) breaks the transmitter down into choline and an acetate ion. The choline is then available for re-

21、uptake into the nerve terminal. These same principles apply to cholinergic transmission at sites other than neuromuscular junctions, although the structure of the synapses differs. In the autonomic nervous system these include nerve-to-nerve synapses at the relay stations (ganglia) in both the sympa

22、thetic and the parasympathetic divisions, and the endings of parasympathetic nerve fibres on non-voluntary (smooth) muscle, the heart, and glandular cells; in response to activation of this nerve supply, smooth muscle contracts (notably in the gut), the frequency of heart beat is slowed, and glands

23、secrete. Acetylcholine is also an important transmitter at many sites in the brain at nerve-to-nerve synapses. To understand how acetylcholine brings about a variety of effects in different cells it is necessary to understand membrane receptors. In post-synaptic membranes (those of the cells on whic

24、h the nerve fibres terminate) there are many different sorts of receptors and some are receptors for acetylcholine. These are protein molecules that react specifically with acetylcholine in a reversible fashion. It is the complex of receptor combined with acetylcholine which brings about a biophysic

25、al reaction, resulting in the response from the receptive cell. Two major types of acetylcholine receptors exist in the membranes of cells. The type in skeletal muscle is known as nicotinic; in glands, smooth muscle, and the heart they are muscarinic; and there are some of each type in the brain. Th

26、ese terms are used because nicotine mimics the action of acetylcholine at nicotinic receptors, whereas muscarine, an alkaloid from the mushroom Amanita muscaria, mimics the action of acetylcholine at the muscarinic receptors. Acetylcholine is the neurotransmitter produced by neurons referred to as c

27、holinergic neurons. In the peripheral nervous system acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. In the central nervous system acetylcholine is believed to be involved in learning, memory, and mood. Acetylcholine is synthe

28、sized from choline and acetyl coenzyme A through the action of the enzyme choline acetyltransferase and becomes packaged into membrane-boundvesicles. After the arrival of a nerve signal at the termination of an axon, the vesicles fuse with the cell membrane, causing the release of acetylcholine into

29、 thesynaptic cleft. For the nerve signal to continue, acetylcholine must diffuse to another nearby neuron or muscle cell, where it will bind and activate areceptorprotein. There are two main types of cholinergic receptors, nicotinic and muscarinic. Nicotinic receptors are located at synapses between

30、 two neurons and at synapses between neurons and skeletal muscle cells. Upon activation a nicotinic receptor acts as a channel for the movement of ions into and out of the neuron, directly resulting indepolarizationof the neuron. Muscarinic receptors, located at the synapses of nerves with smooth or

31、 cardiac muscle, trigger a chain of chemical events referred to as signal transduction. For a cholinergic neuron to receive another impulse, acetylcholine must be released from the receptor to which it has bound. This will only happen if the concentration of acetylcholine in the synaptic cleft is ve

32、ry low. Low synaptic concentrations of acetylcholine can be maintained via a hydrolysis reaction catalyzed by the enzyme acetylcholinesterase. This enzyme hydrolyzes acetylcholine into acetic acid and choline. If acetylcholinesterase activity is inhibited, the synaptic concentration of acetylcholine

33、 will remain higher than normal. If this inhibition is irreversible, as in the case of exposure to many nerve gases and some pesticides, sweating, bronchial constriction, convulsions, paralysis, and possibly death can occur. Although irreversible inhibition is dangerous, beneficial effects may be de

34、rived from transient (reversible) inhibition. Drugs that inhibit acetylcholinesterase in a reversible manner have been shown to improve memory in some people with Alzheimers disease. abstract expressionism, movement of abstract painting that emerged in New York City during the mid-1940s and attained

35、 singular prominence in American art in the following decade; also called action painting and the New York school. It was the first important school in American painting to declare its independence from European styles and to influence the development of art abroad. Arshile Gorky first gave impetus

36、to the movement. His paintings, derived at first from the art of Picasso, Mir, and surrealism, became more personally expressive. Jackson Pollocks turbulent yet elegant abstract paintings, which were created by spattering paint on huge canvases placed on the floor, brought abstract expressionism bef

37、ore a hostile public. Willem de Koonings first one-man show in 1948 established him as a highly influential artist. His intensely complicated abstract paintings of the 1940s were followed by images of Woman, grotesque versions of buxom womanhood, which were virtually unparalleled in the sustained sa

38、vagery of their execution. Painters such as Philip Guston and Franz Kline turned to the abstract late in the 1940s and soon developed strikingly original stylesthe former, lyrical and evocative, the latter, forceful and boldly dramatic. Other important artists involved with the movement included Han

39、s Hofmann, Robert Motherwell, and Mark Rothko; among other major abstract expressionists were such painters as Clyfford Still, Theodoros Stamos, Adolph Gottlieb, Helen Frankenthaler, Lee Krasner, and Esteban Vicente. Abstract expressionism presented a broad range of stylistic diversity within its la

40、rgely, though not exclusively, nonrepresentational framework. For example, the expressive violence and activity in paintings by de Kooning or Pollock marked the opposite end of the pole from the simple, quiescent images of Mark Rothko. Basic to most abstract expressionist painting were the attention

41、 paid to surface qualities, i.e., qualities of brushstroke and texture; the use of huge canvases; the adoption of an approach to space in which all parts of the canvas played an equally vital role in the total work; the harnessing of accidents that occurred during the process of painting; the glorif

42、ication of the act of painting itself as a means of visual communication; and the attempt to transfer pure emotion directly onto the canvas. The movement had an inestimable influence on the many varieties of work that followed it, especially in the way its proponents used color and materials. Its es

43、sential energy transmitted an enduring excitement to the American art scene. Science and technology is quite a broad category, and it covers everything from studying the stars and the planets to studying molecules and viruses. Beginning with the Greeks and Hipparchus, continuing through Ptolemy, Cop

44、ernicus and Galileo, and today with our work on the International Space Station, man continues to learn more and more about the heavens. From here, we look inward to biochemistry and biology. To truly understand biochemistry, scientists study and see the unseen bystudying the chemistry of biological

45、 processes. This science, along with biophysics, aims to bring a better understanding of how bodies work from how we turn food into energy to how nerve impulses transmit.analytic geometry, branch ofgeometryin which points are represented with respect to a coordinate system, such asCartesian coordina

46、tes, and in which the approach to geometric problems is primarily algebraic. Its most common application is in the representation of equations involving two or three variables as curves in two or three dimensions or surfaces in three dimensions. For example, the linear equationax+by+c=0 represents a

47、 straight line in thexy-plane, and the linear equationax+by+cz+d=0 represents a plane in space, wherea, b, c,anddare constant numbers (coefficients). In this way a geometric problem can be translated into an algebraic problem and the methods of algebra brought to bear on its solution. Conversely, th

48、e solution of a problem in algebra, such as finding the roots of an equation or system of equations, can be estimated or sometimes given exactly by geometric means, e.g., plotting curves and surfaces and determining points of intersection. In plane analytic geometry a line is frequently described in

49、 terms of its slope, which expresses its inclination to the coordinate axes; technically, the slopemof a straight line is the (trigonometric) tangent of the angle it makes with thex-axis. If the line is parallel to thex-axis, its slope is zero. Two or more lines with equal slopes are parallel to one

50、 another. In general, the slope of the line through the points (x1,y1) and (x2,y2) is given bym= (y2-y1) / (x2-x1). The conic sections are treated in analytic geometry as the curves corresponding to the general quadratic equationax2+bxy+cy2+dx+ey+f=0, wherea, b, fare constants anda, b,andcare not al

51、l zero. In solid analytic geometry the orientation of a straight line is given not by one slope but by its direction cosines, , , and , the cosines of the angles the line makes with thex-, y-,andz-axes, respectively; these satisfy the relationship 2+2+2= 1. In the same way that the conic sections ar

52、e studied in two dimensions, the 17 quadric surfaces, e.g., the ellipsoid, paraboloid, and elliptic paraboloid, are studied in solid analytic geometry in terms of the general equationax2+by2+cz2+dxy+exz+fyz+px+qy+rz+s=0. The methods of analytic geometry have been generalized to four or more dimensio

53、ns and have been combined with other branches of geometry. Analytic geometry was introduced by RenDescartesin 1637 and was of fundamental importance in the development of thecalculusby Sir Isaac Newton and G. W. Leibniz in the late 17th cent. More recently it has served as the basis for the modern development and exploitation ofalgebraic geometry. circle, closed plane curve consisting of all points at a given distance from some fixed point, called the center. A circle is a conic section cut by a plane perpendicular to the