Mọi người giúp mình 3 câu này nha, sẽ vote

vinhnguyen281164

2 năm trước

Loga Sinh Học lớp 12

0 lượt thích 15 xem

1 trả lời

Thích Trả lời

ngoan0112.2007

a) `-1 <= cosx<=1`

`<=> -3<=3cosx <=3`

`<=> -1 <=2+3cosx <=5`

`=> y_(min) =-1 ; y_(max) =5`.

b) `y=3-4sin^2xcos^2x = 3-2sin2x`

`-1 <= sin2x <=1`

`<=> 1 <= 3-2sin2x <= 5`

`=> y_(min) =1 ; y_(max) =5`.

c) `y=(1+4cos^2x)/3 = 1/3 + 4/3 cos^2x`

`0 <= cos^2x <=1`

`<=> 0 <= 4/3 cos^2x <= 4/3`

`<=> 1/3 <= 1/3 + 4/3 cos^2x <=5/3`

`=> y_(min) =1/3 ; y_(max)= 5/3`.

Vote (0) Phản hồi (0) 2 năm trước

Kuquandx1999

`~rai~`

\(a)y=2+3\cos x\\\text{Ta có:}-1\le \cos x\le 1\\\Leftrightarrow -3\le3\cos x\le 3\\\Leftrightarrow -1\le 2+3\cos x\le 5\\\Leftrightarrow -1\le y\le 5.\\+)Min_y=-1\Leftrightarrow \cos x=-1\Leftrightarrow x=\pi+k2\pi.(k\in\mathbb{Z})\\+)Max_y=5\Leftrightarrow \cos x=1\Leftrightarrow x=k2\pi.(k\in\mathbb{Z})\\\text{Vậy Min}_y=-1\text{ khi x=}\pi+k2\pi;\\\text{Max}_y=5\text{ khi x=}k2\pi.(k\in\mathbb{Z})\\b)y=3-4\sin^2x\cos^2x\\\quad=3-\sin^22x.\\\text{Ta có:}0\le \sin^22x\le 1\\\Leftrightarrow -1\le-\sin^22x\le 0\\\Leftrightarrow 2\le3-\sin^22x\le 3\\\Leftrightarrow 2\le y\le 3.\\+)Min_y=2\Leftrightarrow\sin^22x=1\\\Leftrightarrow \cos^22x=0\\\Leftrightarrow \cos2x=0\\\Leftrightarrow 2x=\dfrac{\pi}{2}+k\pi\\\Leftrightarrow x=\dfrac{\pi}{4}+k\dfrac{\pi}{2}.(k\in\mathbb{Z})\\+)Max_y=3\Leftrightarrow \sin^22x=0\\\Leftrightarrow \sin2x=0\\\Leftrightarrow 2x=k\pi\\\Leftrightarrow x=k\dfrac{\pi}{2}.(k\in\mathbb{Z})\\\text{Vậy Min}_y=2\text{ khi x=}\dfrac{\pi}{4}+k\dfrac{\pi}{2};\\\text{Max}_y=3\text{ khi x=}k\dfrac{\pi}{2}.(k\in\mathbb{Z})\\c)y=\dfrac{1+4\cos^2x}{3}\\\text{Ta có:}0\le\cos^2x\le 1\\\Leftrightarrow 0\le4\cos^2x\le 4\\\Leftrightarrow 1\le1+4\cos^2x\le5\\\Leftrightarrow \dfrac{1}{3}\le\dfrac{1+4\cos^2x}{3}\le\dfrac{5}{3}\\\Leftrightarrow \dfrac{1}{3}\le y\le\dfrac{5}{3}.\\+)Min_y=\dfrac{1}{3}\Leftrightarrow \cos^2x=0\\\Leftrightarrow \cos x=0\\\Leftrightarrow x=\dfrac{\pi}{2}+k\pi.(k\in\mathbb{Z})\\+)Max_y=\dfrac{5}{3}\Leftrightarrow \cos^2x=1\\\Leftrightarrow \sin^2x=0\\\Leftrightarrow \sin x=0\\\Leftrightarrow x=k\pi.(k\in\mathbb{Z})\\\text{Vậy Min}_y=\dfrac{1}{3}\text{ khi x=}\dfrac{\pi}{2}+k\pi;\\\text{Max}_y=\dfrac{5}{3}\text{ khi x=}k\pi.(k\in\mathbb{Z})\)

Vote (0) Phản hồi (0) 2 năm trước

Các câu hỏi liên quan

viết một bài luận nói về đất nước em muốn đến( nước Mỹ nha)

Calli " I miss you 😢 " Tone : đen

giúp mình với ạ,mình cám ơn nhiều!!!

Tam giác ABC có góc A=20 độ, góc B = 30 độ, AB= 60cm. Đường vuông góc kẻ từ C đến AB và cắt AB tại P. Hãy tìm : a) AP ; BP b) CP (cảm ơn mn ạ)

Bài 3: Tính nhanh tổng sau: 6 + 12 + 18 + .......+ 90.

Làm ảnh nền như dưới Y/c: App, đúng size màn hình mt, tone trầm, đẹp, cute ĐỀ rất DỄ làm có tâm vào :))

Bài 3: Tính nhanh tổng sau: 6 + 12 + 18 + .......+ 90.

Giúp mik vs mn sợ sai nên cần mn giúp :<<

Exercise 1: Rewrite the following sentences in reported speech. 1. "Do you like my new clothes?" she asked her friend. -> She asked her friend ________________________________ 2. "Where are my keys?" he asked his wife. -> He asked his wife _____________________________________ 3. "Who is your favourite singer?" Mike asked me. -> Mike asked me ______________________________________ 4. "Where were you?" She asked him. -> She asked him ______________________________________ 5. "Can you pick me up after school?" she asked her mother. -> She asked her mother ________________________________ 6. "Have you seen Kim?" David asked Sarah. -> David asked Sarah __________________________________ 7. "We will have a housewarming party next week," said Mike and Helen. -> Mike and Helen _____________________________________ 8. "Julia and Jose might move to Australia next year," Rory said to us. -> Rory told us _______________________________________ 9. Nam said “I am told to be at school before 7 o’clock” -> Nam said __________________________________________ 10. Thu said “All the students will have a meeting next week” -> Thu said _________________________________________ Exercise 2: Use one of the options to complete the sentences in the reported speech. 1. On Monday: “We will set off tomorrow.” A week later: They said they would set off ……………………………………… a) tomorrow b) the next day 2. In the morning: “I’m going to meet Greg tomorrow.” In the evening: Marion said she was going to meet Greg ……………………….. a) tomorrow b) the following day 3. “I don’t want to put this shelf here.” Mark told me in the bedroom he didn’t want to put …………………………… a) that shelf there b) this shelf there 4. On 1 June: “I invited him last week.” On 10 June: She told me that she had invited him ……………………………… a) the previous week b) last week 5. On Thursday: “We went to see our grandma last week.” On Friday: They said they had gone to see their grandma ……………………… a) the previous week b) last week 6. At school: “We are writing a test today.” After school: Jim told me they were writing a test ……………………………… a) today b) that day 7. “I will resign next week.” Last Friday Tina announced that she would resign …………………………… a) the next week b) the week before

cali chữ: Hoàng Minh Hiếu NL: Cái này dành cho ai đó, chắc ng đó cx bt r ha. Mong mod, ad đừng xóa.

Loga.vn - Cộng Đồng Luyện Thi Trực Tuyến