cho tam giác ABC vuông tại A,AB=1/3 AC.a)Tính góc B,C.

1.Giải pt:

a)\(\sqrt{3x^2+6x+7}+\sqrt{5x^2+10x+4}=4-2x-x^2\)

b)\(x^2+\left(3-\sqrt{x^2+2}\right)x=1+2\sqrt{x^2+2}\)

c)\(\left(x+1\right)\sqrt{x^2-2x+3}=x^2+1\)

d)

Cho tam giác ABC và tia phân giác AD của góc A(D thuộc BC).Gọi M,N lần lượt là chân đường vuông góc kẻ từ B,C tới AD.

CMR:a/\(\frac{BM}{AB}\)=\(\frac{CN}{AN}\)

b/BM+CN≤BC

c/Sin\(\frac{A}{2}\)≤ \(\frac{BC}{AB+AC}\) ≤\(\frac{BC}{2\sqrt{AB+AC}}\)

Không dùng máy tính ,hãy tính:

a)sin18 độ - cos 72 độ

b)\(\frac{tan40đo}{cot44đọ}\)

c)\(sin^225\)độ +\(cos^2\)65 độ

d)tan 37 độ . tan 53 độ

so sánh

a/\(\sqrt{\sqrt{17+12\sqrt{2}}}\)và\(\sqrt{2}+1\)

(\(3-\sqrt{5}\)).\(\sqrt{3}+\sqrt{5}+\left(3+\sqrt{5}\right)\sqrt{3}-\sqrt{5}\)

1.Cho hình thang ABCD có góc A= góc D=90 độ và DB vuông góc BC>Biết AD=12,CD=25.Tính dtich hthang.

2.Cho tam giác ABC Có góc A<90 độ,đường cao BH.Đặt BC=a,CA=b,AC=c',Hc=b'.CM:\(a^2=b^2+c^2-2bc'\)

HOÀN THÀNH CÁC CÂU SAU VỚI CẤU TRÚC USED TO VÀ CÁC ĐỌNG TỪ CHO SẮN:

1.My whole family ___________on my father's salary but now both of my parents work to support our family.

2.My brother _______after me when my parents were at home.

3.In the past,women _____expected to stay home,do household chores and farming instead of getting higher education.

4.Those farmers_______hard but______little money before they were instructed to apply technologies in their farming.

5.We(not)____________out when but now we often do because we are sometimes too busy to prepare a meal.

6.Women(not)___________an important role in the political field in the past 50 years.

7.My uncle_____a sheep farm before he sold it to move to the city.

Viết lại câu sao cho nghĩa k đổi:

1. this was only a small company with saveral years of low profit but now it has changed a lot

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2. men were the breadwinner of the family and women depended greatly on men

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3.my sister admitted that she lied sometimes in the past but now she didn't

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4. Jim asked me that i preferred to do as a child that i no longer did now

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5. who took care of you when you were a toddler?

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6. Jim wasn't interested in reading books when he was small but now he is really into it

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7. i got all the attention from my parents before my little brother was born

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8. bungalows were very popular 6 years ago

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