---Now more and more Chinese senior students are applying for admission to American universities through SAT.
---        . But taking an SAT may cost one more than 10,000 yuan.

如图，在△ABC中，∠C=90°，∠B=30°，以A为圆心，任意长为半径画弧，分别交AB、AC于点M和N，再分别以M、N为圆心，大于$\frac{1}{2}$MN的长为半径画弧，两弧交于点P，连结AP并延长交BC于点D，下列结论：

①AD是∠BAC的平分线；②∠ADB=120°；③AD=BD；④DB=2CD．

其中正确的结论共有（　　）

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    Hi. I am Maya. I am 13 years old. I am from Africa. My father is a teacher and my mother works in a hospital. Now they are working in Beijing. They both like their work and work very hard. My father's favorite animal is the panda, but I like dolphins best.
    I am studying in a middle school. And I like music and drawing best. I want to be a designer. I like to design my room. I like the color pink, so there are a lot of pink things in my room.
    I have three friends in my room. They are Mike, Dora and Peter. They are my toys. I love them. Every night, they sleep with me.

设$a={\int }_0^{\mathrm{\pi }}\left(\sin x+\cos x\right)dx$，则二项式${\left(a\sqrt{x}-\frac{1}{\sqrt{x}}\right)}^5$的展开式中$x^2$项的系数为（   ）

已知函数, 则的值是