[原创]少量几经，大量感想－13日

Angelinacao

能告知这个阅读在哪个GWD中吗？ 谢谢！

dct0401

原题有图，有个4边形ABCD，DA=AB=BC=10，A角90度，B角135度，求面积，选项为
   50，40，100，50√2，50（1+√2），能分成2个直角3角形， 

請問算法???

auweiyagmat

以下是引用dct0401在2006-12-14 20:48:00的发言：

原题有图，有个4边形ABCD，DA=AB=BC=10，A角90度，B角135度，求面积，选项为
   50，40，100，50√2，50（1+√2），能分成2个直角3角形， 

請問算法???

因为角A为直角，DA=AB，DAB为等边直角三角形，面积为 0.5x（10x10）=50，

求得DB为   10√2，

DBA角45度，则DBC为90度 （135-45）画个图可以看得很清楚

三角形DBC面积为 1/2 （DB）（BC）=50 √2

两三角形面积相加的 50（1+√2）

paulfrank11

Q10:

The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

1. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.
           
2. The concentration of mass at the center of M87 is probably a large cluster of dim stars.
           
3. The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.
           
4. The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.

5. The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.

想问楼主为什么这道题的选项A不行

paulfrank11

Q12:

Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?

             

1. The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.
           
2. A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.
           
3. The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.
           
4. Only one other galaxy has been observed to contain gas clouds whirling about its center as they do about the core of M87.
           
5. The gravitational force of a cluster of a billion or so dim stars would be sufficient to cause a whirling ring of gas and dust to collect around the center of a galaxy

还有，12题的答案是选E么？

dot_deng

12题选A

因为原文说了，NGC 4258,有很大的density从而有很大的gravational power， 如果是星体的集合的话，就要求，星体之间很紧密这样反而会是其tearing apart。

那么选项A 说了，有很大的gravational power，但又不会tearing apart，那么显然就不是星体的集合，也就undermine了结论