gwd-11-2

wall_streets

那道小圆内切大圆的题，我怎么还是选A啊，看了以前的讨论没有看懂。

Q2:

D

· B C

A E

In the figure, points A, B, C, D, and E lie on a line. A is on both circles, B is the center of the smaller circle, C is the center of the larger circle, D is on the smaller circle, and E is on the larger circle. What is the area of the region inside the larger circle and outside the smaller circle?

(1) A  B = 3 and BC =2

(2) C D =1 and DE = 4

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

以前讨论说

from2: R=C D+D E=5, r=(R*2-DE)/2=3

这个等式代表什么啊？谢谢！

WalkByFaith

C D+D E=A C=5(大圆半径R)

A C+C D=2r(小圆半径)=5+1=6

r=3 R=5 可以得所求

wall_streets

明白了，谢谢！

zhangzhiming

so , must choose "d"

aster1990

这是陷阱

ETS给的陷阱；因为

A figure accompanying a data sufficiency question will conform to the information given in the question but will not necessarily conform to the additional information given in statements (1) and (2).

但是You may assume that the positions of points, angles, regions, etc. exist in the order shown and that angle measures are greater than zero.

选A选D各自可以自圆其说：

A的话，可以解释为D点可能在CE间，也可能在BC间
D的话，就是D点只能在CE间，如图所示。