（（本小题满分12分）
如图，在四棱锥P—ABCD中，底面ABCD，底面为直角梯形，，且AD=2，AB=BC=1，PA=
（Ⅰ）设M为PD的中点，求证：平面PAB；
（Ⅱ）若二面角B—PC—D的大小为150°，求此四棱锥的体积.

如图，在四棱锥P－ABCD中，底面ABCD是菱形，∠BAD＝，AB＝2，PA＝1，PA⊥平面ABCD，E是PC的中点，F是AB的中点．

（1）求证：BE∥平面PDF；
（2）求证：平面PDF⊥平面PAB；
（3）求三棱锥P－DEF的体积．

如图，在四棱锥P—ABCD中，PA⊥底面ABCD，底面为直角梯形，，且PA=AB=BC=1，AD=2．

（Ⅰ）设M为PD的中点，求证：平面PAB；
（Ⅱ）求侧面PAB与侧面PCD所成二面角的平面角的正切值．

（本小题12分）如图，四棱锥中，
侧面是边长为2的正三角形，且与底面垂直，底面是的菱形，为的中点.
(1)求与底面所成角的大小；
(2)求证：平面；
(3)求二面角的余弦值.

Beijing is facing severe (严重的)  traffic problems."Roads are wider now, but traffic jams (堵塞) often happen every day. " Yuan, a Beijing taxi drivers said.

Beijing government is trying to do something to make traffic jams less.  Before 2007, there were a few subway lines in Beijing. There was only line 1, line 2, line 13 and Batong Line. But now there is line 5, line 10, line 4, the airport fast -track and the Olympic branch line. And there will be 13 subway lines under construction in Beijing at the same time at the end of this year.

The opening of the new subway line is convenient to tourists. Before, arriving in Beijing, many visitors would usually take a taxi to interesting places of Beijing. Today, as soon as people get off the plane, they can take the Airport Express Line, going to different interesting places through the subway lines. The government also strives to open a new line each year from now until 2015. The subway of Beijing reached 300 kilometers in 2010 and it will reach 561 kilometers in 2015.

Miss Xiao, who lives in South Water Bridge and works at Hepingli, said that traveling by her car still took her at least one hour from home to work because of traffic jams. Now, because of the railway line 5, Miss Xiao can arrive at her office in less than haft an hour.

1.What are the trafc problems in Beijing now?

A．Drivers drive too fast.                    B．Roads are not wide enough.

C．Traffic jams often happen.                 D．Traffic lights are always broken.

2.What does the underlined phrase "under construction" mean in Chinese?

A．在学习           B．在建造中          C．在应用中         D．在控制中

3.Why is the opening of the new subway line convenient to tourists?

A．Because the new subway line is very interesting.

B．Because the new subway line's ticket is very cheap.

C．Because people in Beijing can cost less money than that before.

D．Because visitors can take the subway to many different interesting places.

4.Which of the following is TRUE according to the passage?

A．Visitors like to take a taxi in Beijing better.

B．The subway of Beijing will reach 300 kilometers in 2015.

C．There will be 15 subway lines in Beijing at the end of the year.

D．It takes Miss Xiao less time to get to her workplace by railway line 5.

5.What is the main idea of the passage?

A．People in Beijing invented high -speed trains.

B．Railway lines in Beijing only covers some areas.

C．Beijing welcomes visitors from different places.

D．Beijing government has done something to make traffic jams less.