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如图,在等腰三角形ABC中,∠BAC=120°,AB=AC=2,点D是BC边上的一个动点(不与B、C重合),在AC上取一点E,使∠ADE=30°.

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C
    There are an extremely large number of ants worldwide. Each individual ant hardly weigh anything, but together they weigh almost the same as all of mankind. They also live nearly everywhere, except on frozen mountain tops or around the Antarctic. For animals their size, ants have been surprisingly successful, largely due to their wonderful social conduct.
    In groups that vary in size from a few hundred to tens of millions, they organize their lives with a clear distribution of labor. Even more amazing is how they achieve this level of organization. While we use sound and sight to communicate, ants depend mostly on pheromone (信息素), which is a kind of chemical released by individuals and smelled or tasted by fellow members of a group. When an ant finds food, it produces a pheromone that will lead others straight to where the food is. When an ant comes under attack or is dying, it sends out an alarm pheromone to warn the whole group to prepare for a defensive fight.
    In fact, when it comes to the art of war, ants have no equal. They are completely fearless and will take on an animal much larger than themselves, attacking in large groups and beating their target. They show so much devotion to their group that not only soldier ants but also worker ants will sacrifice their lives to help defeat an enemy.
    United and devoted, these little animals have survived on the earth for more than 140 million years, far longer than dinosaurs. Because they think as one, they have a united intelligence greater than you would expect from one small individual ant.

同类题4

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    Five years ago, when I taught art at a school in Seattle, I used Tinkertoys as a test at the beginning of a term to find out something about my students. I put a small set of Tinkertoys in front of each student, and said: “Make something out of the Tinkertoys. You have 45 minutes today - and 45minutes each day for the rest of the week.”

    A few students hesitated to start. They waited to see the rest of the class would do. Several others checked the instructions and made something according to one of the model plans provided. Another group built something out of their own imaginations.

    Once I had a boy who worked experimentally with Tinkertoys in his free time. His constructions filled a shelf in the art classroom and a good part of his bedroom at home. I was delighted at the presence of such a student. Here was an exceptionally creative mind at work. His presence meant that I had an unexpected teaching assistant in class whose creativity would infect(感染) other students.

    Encouraging this kind of thinking has a downside. I ran the risk of losing those students who had a different style of thinking. Without fail one would declare, “But I'm just not creative.”

    “Do you dream at night when you're asleep?”

    “Oh, sure.”

    “So tell me one of your most interesting dreams.” The student would tell something wildly imaginative. Flying in the sky or in a time machine or growing three heads. “That's pretty creative. Who does that for you?”

    “Nobody. I do it.”

    “Really-at night, when you're asleep?”

    “Sure.”

    “Try doing it in the daytime, in class, okay?”