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问题 选择题

三角形三个内角的度数之比分别为（1）2：3：4；（2）2：2：4；（3）3：4：5；（4）2：3：5．其中是直角三角形的个数为（　　）

A．1

B．2

C．3

D．4

答案

（1）∵三角形三个内角的度数之比分别为2：3：4

∴设三角形的三个内角分别为2x，3x，4x，

∵三角形的内角和是180°，

∴2x+3x+4x=180°，解得x=20°，

∴4x=4×20°=80°，

∴此三角形是锐角三角形，故本小题错误；

（2））∵三角形三个内角的度数之比分别为2：2：4

∴设三角形的三个内角分别为2x，2x，4x，

∵三角形的内角和是180°，

∴2x+2x+4x=180°，解得x=22.5°，

∴4x=4×22.5°=90°，

∴此三角形是直角三角形，故本小题正确；

（3））∵三角形三个内角的度数之比分别为3：4：5，

∴设三角形的三个内角分别为3x，4x，5x，

∵三角形的内角和是180°，

∴3x+4x+5x=180°，解得x=15°，

∴5x=5×15°=75°，

∴此三角形是锐角三角形，故本小题错误；

（4））∵三角形三个内角的度数之比分别为2：3：5

∴设三角形的三个内角分别为2x，3x，5x，

∵三角形的内角和是180°，

∴2x+3x+5x=180°，解得x=18°，

∴5x=5×18°=90°，

∴此三角形是直角三角形，故本小题正确．

故选B．

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Bush’s MBA


Twenty-six of 42 presidents, including Bill Clinton, were lawyers. Seven were generals. George W. Bush becomes the first with an MBA.
Those who have had Bush for a boss since the mid-1980s—in the (1) of oil, baseball and Texas state government—describe his management (2) as straight from the pages of the organizational-behavior (3) he studied while getting his masters of business administration (4) at Harvard University in 1975.
He manages by what is known (5) "walking around," having learned that sitting behind a desk and passing out memos does (6) to energize anyone.
He has a reputation for fueling "creative tension" (7) his subordinates, encouraging them to take and defend opposing (8) . That sacrifices harmony, but puts ideas to the test and lets Bush (9) above the fray, where he can offer guidance instead of barking (10) . Imagine the creative tension that may erupt (11) the likes of Secretary of State-designate Colin Powell and Defense Secretary— (12) Donald Rumsfeld.
Above all, former employees say that he is a master at delegating (13) installing measures of accountability—ways of knowing (14) subordinates are getting the job done without looking (15) any shoulders. That frees Bush for strategic thinking—perhaps (16) two words hammered into MBA students most—which means thinking (17) to seize opportunities and to derail threats to the best of plans.
"George was my (18) ," says Tom Schieffer, who served as president of the Texas Rangers under Bush (19) 1991 and 1995. "But he never made me feel that way. He went out of his way to treat me as a (20) , not a subordinate."
That’s one trait that might be of concern, says Michael Useem, director of the Wharton Center for Leadership and Change at the University of Pennsylvania. It’s important for subordinates to feel part of the team, but not just because the boss craves popularity. Just as in the military, it must be understood who is in charge when the final order is given.
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