Cho ∆ABC vuông tại A, có AB = 6cm, AC = 8cm. 1) Tính số đo góc B, góc C (làm tròn đến độ) và đường cao AH. 2) Chứng minh rằng: AB. cosB + AC. cosC = BC. 3) Trên cạnh AC lấy điểm D sao cho DC = 2DA. Vẽ DE vuông góc với BC tại E. Chứng minh rằng: 1/AB^2 + 1/AC^2 = 4/9DE^2 ----->>>mình đang cần gấp

help me..............................!!!

1. In order to cook balck-peas sweet gruel, we need some ingredients like this: some black peas, of course, some sugar, fresh water, and some……………to extract its milk to make the soup tastier.

giải giúp mình vs ...mình cảm ơn

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1.What are they doing? – They are…………. with paper boat. A. doing B.playing C. making 2. Has she got any pet? – No, she…………. A. has B. haven’t C. hasn’t 3. How many………… are there in your bedroom? – There are two. A. chair B. chairs C. x 4. What’s Mai doing? – She…………….. A. play cycling B. is cycling C. cycles 5. How old is your…………….? – He’s thirty-four. A. sister B. mother C. father 6. What is the…………… today? A.activity B. colour C. weather 7……………many cats do you have? A. Why B. How C. What 8. what ……………….are your dogs? – They are black and white. A. colour B. yellow C. sunny

Bài 10: Cho A = 1 + 3 + 3^2 + 3^3 + 3^4 + 3^5 + 3^6 + 3^7 a, Tính 3A b, Chứng minh A = (3^8 - 1) : 2 Bài 11: Cho Q = 1 + 3 + 3^2 + ... + 3^2006 a, tính 3q b, chứng minh q = ( 3^2007 - 1) : 2

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