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问题 解答题
已知定点A（12.0），M为曲线
x=6+2cosθ
y=2sinθ
上的动点，若
AP
=2
AM
，试求动点P的轨迹C的方程．
答案

设M（6+2cosθ，2sinθ），动点（x，y）

由

AP
=2
AM
，即M为线段AP的中点

故6+2cosθ=

x+12
2
，2sinθ=
y+0
2

即

x=4cosθ
y=4sinθ
即x2+y2=16

∴动点P的轨迹C的方程为x2+y2=16

单项选择题

One method of dating the emergence of species is to compare the genetic material of related species. Scientists theorize that the more genetically similar two species are to each other, the more recently they diverged from a common ancestor. After comparing genetic material from giant pandas, red pandas, raccoons, coatis, and all seven bear species, scientists concluded that bears and raccoons diverged 30 to 50 million years ago. They further concluded that red pandas separated from the ancestor of today’s raccoons and coatis a few million years later, some 10 million years before giant pandas diverged from the other bears.
Which one of the following can be properly inferred from the passage

A．Giant pandas and red pandas are more closely related than scientists originally thought they were.

B．Scientists now count the giant panda as the eighth species of bear.

C．It is possible to determine, within a margin of just a few years, the timing of divergence of various species.

D．Scientists have found that giant pandas are more similar genetically to bears than to raccoons.

E．(E) There is substantial consensus among scientists that giant pandas and red pandas are equally related to raccoons.
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单项选择题 A1/A2型题

产后病的主要病理特点是：（）

A.气血虚弱

B.阴虚血热

C.多虚多瘀

D.寒热并见

E.气机郁滞
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