Giải thích các bước giải:
Áp dụng công thức hàm số cos trong tam giác ta có:
\(\begin{array}{l}\cos A = \frac{{{b^2} + {c^2} - {a^2}}}{{2bc}} = \frac{{{{10}^2} + {{13}^2} - {8^2}}}{{2.10.13}} = \frac{{41}}{{52}} \Rightarrow \widehat A = 37^\circ 57'\\\cos B = \frac{{{a^2} + {c^2} - {b^2}}}{{2ac}} = \frac{{{8^2} + {{13}^2} - {{10}^2}}}{{2.8.13}} = \frac{{133}}{{208}} \Rightarrow \widehat B = 50^\circ 15'\\\widehat C = 180^\circ - \widehat A - \widehat B = 91^\circ 48'\end{array}\)
Áp dụng công thức đường trung tuyến trong tam giác ta có:
Độ dài đường trung tuyến CM là:
\(\begin{array}{l}C{M^2} = \frac{{{a^2} + {b^2}}}{2} - \frac{{{c^2}}}{4} = \frac{{{8^2} + {{10}^2}}}{2} - \frac{{{{13}^2}}}{4} = \frac{{159}}{4}\\ \Rightarrow CM = \frac{{\sqrt {159} }}{2}\end{array}\)
Đáp án:
a) Áp dụng đly hàm số cos
c2=a2+b2−2abcosAc2=a2+b2−2abcosA
<−>2abcosA=a2+b2−c2<−>2abcosA=a2+b2−c2
<−>2.8.10.cosA=82+102−132<−>2.8.10.cosA=82+102−132
<−>cosA=−132<−>cosA=−132
Ta thấy cosA<0cosA<0, do đó ˆA>90∘A^>90∘.
Vậy tam giác ABC tù tại A.
b) Áp dụng công thức ta có
ma=√2b2+2c2−a24=√4742ma=2b2+2c2−a24=4742
Áp dụng công thức Hê - rông ta có
SABC=√p(p−a)(p−b)(p−c)=√255754
cho hai điểm P(6;1) và Q(-3;-2) và đường thẳng Δ:2x-y-1=0 tìm tọa độ điểm M thuộc Δ sao cho MP+MQ nhỏ nhất
Trình bày cơ cấu ngành trồng trọt
tìm n thuộc N sao cho: a) 10 chia hết cho n ; b)(n+2) là ước của 20 ; c) 12 chia hết (n-1) ;d) (2n+3) là ước của 10
Cho tam giác ABC có 3 góc nhọn nội tiếp đường tròn O. Các đường cao AD ; CF ; BE cắt nhau tại H và cắt đg tròn O lần lượt tại M, N,P Cm : Tứ giác CEHD nội tiếp 4 điểm D , C,E,F cùng nằm trên đường tròn
Worksheet 2 I. Odd one out 1. A. watch B. play C. swim D. sport 2. A. running B. fishing C. skiing D. telling 3. A. basketball B. volleyball C. football D. chess 4. A. ball B. kick C. score D. goal 5. A. hit B. catch C. throw D. net II. Choose the best answer 1. You have to throw the ball into the net when you play . A. basketball B. football C. tennis D. badminton 2. My sister often badminton in her free time. A. play B. plays C. playing D. to play 3. “ do you do judo?” – “Twice a week” A. When B. Where C. How often D. Why 4. draw on the walls and tables, please. A. Do B. Don’t C. Should D. Shouldn’t 5. Last summer, I fishing with my uncle in the afternoon. A. go B. went C. goes D. going 6. I like watching football matches, but I am not very good playing football. A. at B. in C. on D. for 7. We to Ho Chi Minh City for our last summer vacation. A. go B. went C. goed D. will go 8. Liz buy a lot of souvenirs for her friends? A. Did B. Do C. Were D. Wasn’t III. Put the verb in bracket in correct form 1. When my brother and I (be) small, we (go) swimming every weekend. 2. Minh (not go) jogging yesterday; she (stay) at home and (do) aerobics. 3. Owen is a football coach but he (not work) at the moment. 4. You (watch) the tennis match on TV last night? 5. My mother (make) a dress now. 6. She never (stay) up late at night. 7. I (meet) her at the movie theater last night. 8. Two years ago, she (teach) Maths at a Secondary school. IV. Write imperatives or request sentences Eg: You should go to bed early. Go to bed early. You should not stay up late. Don’t stay up late. 1. You should brush your teeth after meals. 2. You should not play soccer in the street. 3. You should wash and iron your own clothes. 4. You should not eat too much candy. 5. You should wash your hands before meals. 6. You should not worry about the examination. 7. You should tidy your room every day. 8. You should not forget to write to your parents. V. Write sentences using the given words 1. They/ live here/ two years ago. 2. Nga/ be late for school/ yesterday morning. 3. She/ buy/ a lot of souvenirs/ last summer vacation. 4. My mother/ give/ me/ yellow cap. 5. They/ arrive/ the airport/ eight o’clock/ this morning. VI. Make question for underlined part 1. He often does his homework in the evening. 2. I usually play soccer after school. 3. We are going to stay there for a week. 4. Minh goes swimming with his friends. 5. It is 2 kilometers from my house to the market. VII. Rewrite the following sentences without changing the meaning of the first one 1. No sport in Britain is as popular as football. Football 2. It’s good for you to do morning exercise regularly. You 3. David likes playing badminton most. Badminton *4. Sports and games are very important in children’s lives. Sport and games play 5. Simon is very good at basketball. Simon giúp em với!!!
Cho em xin lời giải của Phần C,Reading ý a ak
(192-37+85) -85+192 cần giải gấp ạ
Làm cho mình câu b bài 3 nha vote 5 sao
Mọi ng giúp em bài 4,6 ạ, em xin chân thành cảm ơn
Cho phương trình (ẩn x) x2_2mx+m2+3m-18=0(*) (với m là tham số). Tìm giá trị của tham số m để phương trình (*) có hai nghiệm phân x1;x2 thỏa mãn 3x1-x2=12
Loga.vn - Cộng Đồng Luyện Thi Trực Tuyến
