题干

如图,为了测量河宽,在河的一边沿岸边选取B、C两点,在对岸岸边选择点A.测得∠B=45°,∠C=60°,BC=30米.求这条河的宽度(这里指点A到直线BC的距离).(结果精确到1米,参考数据2≈1.4,3≈1.7)

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同类题4

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    Can you imagine(想象) you can fish in your house on a cold winter day? Now we are going to tell you about a special kind of house—the ice(冰) fishing house. Staying in a house like that, you can even do the fishing and watch TV at the same time!

    In North America and North Europe (北欧),many people like fishing on the ice in cold winter. But it's too cold to stay in the open air, so people think of making an ice fishing house. The house is right on the ice. The ice must be strong enough to carry it. In the house, people can dig(挖) some holes in the ice and begin fishing. People can have a lot of fun in their ice fishing houses. In the houses, there are enough things for everyday use. Some even have a bedroom, a kitchen and a toilet. How comfortable! After fishing, people can cook the fish and enjoy their dinner.

    Today, most of the ice fishing houses can move(移动). They are made of light materials. Some ice fishing houses can move after fishing. Would you like to have a stay in an ice fishing house? You will like it!

A ____ kind of house-Ice fishing house(冰钓屋)

____ do people make ice fishing houses?

It's ____ cold to stay outside in cold winter.

How are the houses?

The houses are on the ice and the ice is ____ enough to carry them.

They are made of ____ materials.

Some of them can move ____ fishing.

What can people do in the houses?

People can do the fishing ____ watching TV.

People can cook the ____ and enjoy their ____.

People can live a ____ life with a bedroom, a kitchen and a toilet.