已选分类
理学数学
单选题如图6-61，正方形ABCD的对角线AC、BD交于点M，且分正方形为四个三角形，O1，O2，O3，O4分别为△AMB、△BMC、△CMD、△DMA的内切圆圆心，已知AB=1，则图中阴影部分的面积为()．
单选题设则x=0是f(x)的()
单选题微分方程y"=3x的通解是()。
单选题已知函数f(x)具有任意阶导数，且f"(x)=[f(x)]
2
，则当n为大于2的正整数时
单选题若当x→0时，e
tan x
～e
x
与x
n
是同阶无穷小量，则n=______
单选题设f(x)可导，则下列正确的是______．A．B．C．D．
单选题快慢两列车长度分别为160米和120米，它们相向行驶在平行轨道上，若坐在慢车上的人见整列快车驶过的时间是4秒，那么坐在快车上的人见整列慢车驶过的时间是______．
单选题设A，B为三阶矩阵且A不可逆，又AB+2B=O且r(B)=2，则|A+4E|=______．
单选题等腰三角形的腰长为5，底边长为6，求内切圆的半径．
单选题设f(x)连续，且，则F"(x)=______．A．B．C．D．
单选题中国共产党十六大报告指出，贯彻“三个代表”重要思想，本质在______。 A．坚持以经济建设为中心 B．坚持四项基本原则 C．坚持改革开放 D．坚持执政为民
单选题若函数f(x)=ln(3x)，则f"(2)等于______。A．6B．ln6C．D．
单选题设则在(-∞，+∞)内，下列正确的是______
单选题约等于几?
单选题已知A为三阶方阵，1，1，2是A的三个特征值，α
1
，α
2
，α
3
分别为对应的三个特征向量，则______
单选题
单选题设y=lnx，则y"=()
单选题从水平放置的球体容器的顶部的一个孔向球内以相同的速度注水．容器中水面的高度与注水时间t之间的关系用图像表示应为()．(E)以上均不正确
单选题A weather map is an important tool for geographers. A succession of three of four maps presents a continuous picture of weather changes. Weather forecasts are able to determine the speed of air masses and fronts; to determine whether an individual pressure area is deepening or becoming shallow and whether a front is increasing or decreasing in intensity. They are also able to determine whether an air mass is retaining its original characteristics or taking on those of the surface over which it is moving. Thus, a most significant function of the map is to reveal a synoptic picture of conditions in the atmosphere at a given time. All students of geography should be able to interpret a weather map accurately. Weather maps contain an enormous amount of information about weather conditions existing at the time of observation over a large geographical area. They reveal in a few minutes what otherwise would take hours to describe. The United States weather Bureau issues information about approaching storms, floods, frosts, droughts, and all climatic conditions in general. Twice a month it issues a 30-day "outlook" which is a rough guide to weather conditions likely to occur over broad areas of the United States. These 30-day outlooks are based upon an analysis of the upper air levels with often set the stage for the development of air masses, fronts, and storms. Considerable effort is being exerted today to achieve more accurate weather predictions. With the use of electronic instruments and earth satellites, enormous gains have taken place recently in identifying and tracking storms over regions which have but few meteorological stations. Extensive experiments are also in progress for weather modification studies. But the limitations of weather modification have prevented meteorological results except in the seeding of super-cooled, upslope mountainous winds which have produced additional orographical precipitation on the windward side of mountain ranges. Nevertheless, they have provided a clearer understanding of the fundamentals of weather elements.
单选题AB和CD为平面内两条相交直线，AB上有m个点，CD上有n个点，且两直线上各有一个与交点重合，则以这m+n-1个点为顶点的三角形的个数是()．