题干

如图,在△ABC中,AB=AC,将△ABC绕顶点B顺时针旋转,得到△A′BC′.设∠A=α,当A′C′恰好经过顶点C时,∠A′BC=____(用含α的式子表示).

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90°﹣
3
α
2

同类题3

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    If you want to convince the boss you deserve a pay rise or promotion, the solution could be simple—eat the same food as they do. Psychologists have discovered managers are much more likely to instantly trust us if we choose the same dishes as them.

    During experiments, discussions over wages and work conditions were much more successful if both sides chose to snack on the same treats. And shoppers were much more likely to buy a product advertised on TV by someone eating a similar food to them at the time.

    The reason is thought to be so-called similarity attraction theory — where people tend to like others who have similar tastes or habits to themselves. But this is believed to be one of the first studies highlighting the role of food in this relationship. Researchers at Chicago University in the US conducted a series of experiments to examine food's role in earning trust.

    In a test, participants were told to watch TV — where someone pretending to be a member of the public praised a certain product. The volunteers were given Kit Kat(巧克力) bars to nibble(轻咬), while the TV people ate either a Kit Kat or grapes as they talked.

    The results showed viewers were much more likely to express an interest in buying the product if the TV showed the other person eating a Kit Kat too.

    The researchers added, ―Although similarity in food consumption is not a sign of whether two people will get along, we find consumers treat this as such. They feel more trusting of those who consume as they do. It means people can immediately begin to feel friendship and develop a bond, leading to smoother transactions from the start.

    Harley Street psychologist Dr Lucy Atcheson said it was already known that wearing similar clothes could instantly create trust. But this was the first report that food had the same effect. She said, This is really interesting. It makes sense as people feel they have common ground and can trust the other person. That means negotiations are more likely to be successful.

同类题5

某课外研究小组,用含有较多杂质的铜粉,通过不同的化学的反应制取胆矾.其设计的实验过程为:

(1)铜中含有大量的有机物,可采用灼烧的方法除去有机物,灼烧时将瓷坩埚置于____ 上(用以下所给仪器的编号填入,下同),取用坩埚应使____ ,灼烧后的坩埚应放在____ 上,不能直接放在桌面上.

实验所用仪器:a.蒸发皿   b.石棉网   c.泥三角    d.表面皿    e.坩埚钳   f.试管夹

(2)杂铜经灼烧后得到的产物是氧化铜及少量铜的混合物,用以制取胆矾.灼烧后含有少量铜的可能原因是 ____ .

a.灼烧过程中部分氧化铜被还原        b.灼烧不充分铜未被完全氧化

c.氧化铜在加热过程中分解生成铜      d.该条件下铜无法被氧气氧化

(3)通过途径II实现用粗制氧化铜制取胆矾,必须进行的实验操作步骤:酸溶、加热通氧气、过滤、____ 、冷却结晶、____ 、自然干燥.

(4)由粗制氧化铜通过两种斜径制取胆矾,与途径I相比,途径II有明显的两个优点是:____ 、____ .

(5)在测定所得胆矾(CuSO4•xH2O)中结晶水x值的实验过程中,若测定结果x 值偏高,可能的原因是____ .

a.加热温度过高                  b.胆矾晶体的颗粒较大

c.加热后放在空气中冷却          d.胆矾晶体部分风化.