问答题求微分方程y′+ycosx=(lnx)e -sinx 的通解．

问答题Practically speaking, the artistic maturing of the cinema was the single-handed achievement of David W. Griffith (1875-1948). (46)Before Griffith, photography in dramatic films consisted of little more than placing the actors before a stationary camera and showing them in full length as they would have appeared on stage. From the beginning of his career as a director, however, Griffith, because of his love of Victorian painting, employed composition. He conceived of the camera image as having a foreground and a rear ground, as well as the middle distance preferred by most directors. By 1910 he was using close-ups to reveal significant details of the scene or of the acting and extreme long shots to achieve a sense of spectacle and distance. His appreciation of the camera' s possibilities produced novel dramatic effects. (47) By splitting an event into fragments and recording each from the most suitable camera position, he could significantly vary the emphasis from camera shot to camera shot. Griffith also achieved dramatic effects by means of creative editing. By juxtaposing images and varying the speed and rhythm of their presentation, he could control tile dramatic intensity of the events as the story progressed. (48) Despite the reluctance of his producers, who feared that the public would not be able to follow a plot that was made up of such juxtaposed images, Griffith persisted, and experimented as well with other elements of cinematic syntax that have become standard ever since. These included the flashback, permitting broad psychological and emotional exploration as well as narrative that was not chronological, and the crosscut between two parallel actions to heighten suspense and excitement. In thus exploiting fully the possibilities of editing, Griffith transposed devices of the Victorian novel to film and gave film mastery of time as well as space. Besides developing the cinema's language, Griffith immensely broadened its range and treatment of subjects. (49) His early output was remarkably eclectic: it included not only the standard comedies, melodramas, westerns, and thrillers, but also such novelties as adaptations from Browning and Tennyson, and treatments of social issues. As his successes mounted, his ambitions grew, and with them the whole of American cinema. When he remade Enoch Arden in 1911, he insisted that a subject of such importance could not be treated in the then conventional length of one reel. Griffith' s introduction of the American-made multi-reel picture began an immense revolution. Two years later, Judith of Bethulia, an elaborate historic philosophical spectacle, reached the unprecedented length of four reels, or one hour' s running time. (50) From our contemporary viewpoint, the pretensions of this film may seem a little ridiculous, but at the time it provoked endless debate and discussion and gave a newintellectual respectability to the cinema.

问答题设曲线y=f(x)上任一点(x，y)处的切线斜率是，且该曲线经过点

问答题作变换t=tanx把微分方程变换成y关于t的微分方程，并求原微分方程的通解．

问答题设求微分方程=Q(x)(x∈[0，+∞)，x≠1)满足初始条件y(0)=0的连续解．

问答题设函数u的全微分du=[ex+f'(x)]ydx+f'(x)dy，其中f在(-∞，+∞)内具有二阶连续的导数，且f(0)=4，f'(0)=3，求f(x)．

问答题已知f"(x)=1+x 2 ，且f(0)=1，求f(x)．

问答题设f(x)二阶连续可导，且f(0)=0，f'(0)=1，求u(x，y)，使 du=y[f(x)+3e2x]dx+f'(x)dy．

问答题求满足初始条件y|x=1=0的特解．

问答题设函数f(x)在(-∞，+∞)内有连续导数，且满足求f(t)．

问答题若一曲线上任一点M(x，y)处的切线斜率为，且过点，求此曲线方程．又当x取何值时，切线的斜率为．

问答题设函数f(x)在[0，+∞)上可导，且f(1)=3，若f(x)的反函数g(x)满足求f(x)．

问答题设f(x)连续，又满足，求f(x)．

问答题求微分方程y"+4y'+4y=cos2x满足条件y(0)=y'(0)=0的特解．

问答题子弹以速度v0=200米/秒与板垂直的方向打入厚度为10米的板，穿过后以速度v1=80米/秒离开此板，设板对子弹l拘阻力与速度平方成正比，求子弹穿过板5米厚时的速度．

问答题求的通解．

问答题Directions:Writeanessayof160-200wordsbasedonthefollowingdrawing.Inyouressay,youshould1)describethedrawingbriefly,2)explainitsintendedmeaning,andthen3)giveyoursuggestionsastothebestwaytoencouragehonesty.YoushouldwriteneatlyonANSWERSHEET2.诚信如照镜子，你以真面目对它，它报以真面目，你以假面目对它，它也还你假面目。

问答题求微分方程满足初始条件的特解．

问答题解下列微分方程

问答题设有连接点O(0，0)和A(1，1)的一段凸的曲线弧上的任一点P(x，y)，曲线弧与直线段所围图形的面积为x2，求曲线弧的方程．