【正文】
m. Then we plement the differential mean value theorem of twovariable function in textbook following one variable function, give the expressions of Rolle theorem, Cauchy mean value theorem, Taylor mean value theorem of twovariable function, constitute auxiliary function and give the proof procedure, discuss the geometric significance of the Rolle theorem and Lagrange theorem of twovariable function. Later, we give the expressions of the Rolle theorem, Lagrange theorem, Cauchy mean value theorem, Taylor mean value theorem of n variable function by paring the differential mean value theorem of onevariable function and twovariable function. Similarly, by constituting auxiliary function, we change nvariable function into onevariable function and give the proof of four theorems. Check the availability of the differential mean value theorem by some typical examples. At last, proceed from the differential mean value theorem of twovariable function, we give the expressions of Rolle theorem, Lagrange theorem, Cauchy mean value theorem in plex field and check the availability of the differential mean value theorem by some typical examples at the same time.Keywords: nvariable function。 plex field引 言微分中值定理是微分學(xué)的核心定理,它是聯(lián)系函數(shù)與導(dǎo)數(shù)的橋梁,微分中值定理把函數(shù)在某個(gè)區(qū)間上的函數(shù)值與其導(dǎo)數(shù)值聯(lián)系起來,應(yīng)用局部狀態(tài)的導(dǎo)數(shù)研究函數(shù)在區(qū)間上的“整體”性態(tài),它是研究函數(shù)性態(tài)的重要工具.在大學(xué)四年的學(xué)習(xí)中,已經(jīng)掌握了一些有關(guān)一元微分中值定理的內(nèi)容,我們知道一元函數(shù)的羅爾定理,拉格朗日定理,柯西中值定理,泰勒中值定理分別建立了函數(shù)與一階導(dǎo)數(shù)的關(guān)系和函數(shù)與高階導(dǎo)數(shù)的關(guān)系.在實(shí)際應(yīng)用中,很多情況要突破一元微分學(xué)和平面領(lǐng)域這些局限,為了更好的利用微分學(xué)中值定理這個(gè)重要工具,需要把它的應(yīng)用范圍加以擴(kuò)展,使之能夠在元微分學(xué)即維空間以及復(fù)數(shù)域上得以使用.本文將分三部分對(duì)微分中值定理進(jìn)行推廣,第一部分中,首先從數(shù)學(xué)分析教材入手,梳理教材中學(xué)過的有關(guān)一元函數(shù)微分中值定理的相關(guān)內(nèi)容,進(jìn)而研究一元函數(shù)羅爾定理,拉格朗日定理,柯西中值定理,泰勒中值定理之間的關(guān)系,試圖找出統(tǒng)一的中值公式,通過這個(gè)公式全面認(rèn)識(shí)這四個(gè)定理.其次,對(duì)照一元函數(shù)微分中值定理的分析研究,探討二元函數(shù)羅爾定理,拉格朗日定理,柯西中值定理,二元函數(shù)泰勒中值定理的形式及成立的條件,然后探討定理之間的關(guān)系,找到統(tǒng)一的中值公式,透過這個(gè)公式再認(rèn)識(shí)微分中值定理,接著仿照一元函數(shù)微分中值定理給出證明及其幾何意義.第二部分中,對(duì)比一元函數(shù)與二元函數(shù)微分中值定理,給出元函數(shù)微分中值定理的成立條件和中值公式,同樣通過構(gòu)造“輔助函數(shù)”證明定理成立,并自由想象多元函數(shù)微分中值定理的幾何意義.第三部分中,從二元函數(shù)微分中值定理入手,仿照二元函數(shù)中值定理的形式,探討微分中值定理在復(fù)數(shù)域上的表述.接著再通過構(gòu)造“輔助函數(shù)”給出定理證明.1 傅立葉級(jí)數(shù)自然界中周期現(xiàn)象的數(shù)學(xué)描述就是周期函數(shù).最簡(jiǎn)單的周期現(xiàn)象,如單擺的擺動(dòng)等,都可以用正玄函數(shù)或余弦函數(shù)表示.但是,復(fù)雜的周期現(xiàn)象,