Предмет: Алгебра, автор: Tasting

1.Вычислите
2. Упростите выражение

Приложения:

Ответы

Автор ответа: fedorkapomidorka2004

1

сделал решение на листе бумаги, надеюсь все понятно

Приложения:

Автор ответа: Applegate

7

Ответ:

$\displaystyle 1)tg\alpha=-1\frac{1}{3} ,sin\frac{\alpha}{2} =\frac{2}{\sqrt{5} } ,cos2\alpha=-0,28;\\2)~1$

Объяснение:

$\boxed{1}\\\displaystyle \sf DANO:\\cos\alpha=-\frac{3}{5} ;~~\frac{\pi }{2} < \alpha < \pi \Rightarrow a\in(90^\circ;180^\circ)\\----------\\tg\alpha=? \\sin\frac{\alpha}{2} =?\\cos2\alpha=?\\----------\\sin\frac{\alpha}{2} =\sqrt{\frac{1-cos\alpha}{2} } =\sqrt{\frac{\frac{5}{5} +\frac{3}{5}}{2} } =\sqrt{\frac{\frac{8}{5} }{2} } =\sqrt{\frac{4}{5} } =\frac{2}{\sqrt{5} } ;\\sin^2\alpha+cos^2\alpha=1\Rightarrow \\\Rightarrow sin\alpha=\sqrt{1-cos^2\alpha}=\sqrt{\frac{25}{25} -\frac{9}{25} } =$

$\displaystyle \sf =\sqrt{\frac{16}{25} } =\frac{4}{5} =0,8;\\cos2\alpha=cos^2\alpha-sin^2\alpha=\frac{9}{25} -\frac{16}{25} =-\frac{7}{25} =-0,28;\\tg\alpha=\frac{sin\alpha}{cos\alpha} =\frac{\frac{4}{5} }{-\frac{3}{5} }=\frac{4}{5} *\bigg(-\frac{5}{3} \bigg)=-4/3=-1\frac{1}{3}$

$\boxed{2}$

$\displaystyle \frac{sin2\alpha}{1-cos2\alpha} *tg\alpha=\frac{2sin\alpha cos\alpha}{1-(1-2sin^2\alpha)} *tg\alpha=\frac{2sin\alpha cos\alpha sin\alpha}{2sin^2\alpha cos\alpha} =\frac{sin\alpha cos\alpha}{sin\alpha cos\alpha} =\frac{cos\alpha}{cos\alpha} =1$

Предыдущий вопрос

Следующий вопрос

Интересные вопросы

Предмет: Английский язык, автор: Juliaosipova1703

Выберите правильный вариант модального глагола и подставьте в предложение. Предложения переведите.

1. If I don’t study for the next test, I ____ fail it.
a) ought to; b) should; c) might; d) will have to.
2. It ____ be Jack. He drives a Fiat and this guy is driving a Jaguar.
a) can’t; b) should; c) ought to; d) might.
3. He ___ to go to the dentist because he has toothache.
a) ought; b) must; c) should; d) have.
4. It was a very difficult text. I ____ look up a lot of words in the dictionary.
a) must; b) have to; c) had to; d) must to.
5. If we ___ study, we could go out.
a) didn’t have to; b) had to study; c) could; d) didn’t have.

2 года назад

Предмет: Английский язык, автор: nastyanastya715

Помогите, пожалуйста. Заранее спасибо))

Use the verbs in Past Perfect, Past Indefinite or Past Continuous, read and translate the sentences:
1. They (to translate) the text by the time the teacher (to come).
2. I (to write) the essay by 12 o'clock.
3. He (to write the essay the day before yesterday.
4. I (to phone) her at seven o'clock last night. She...already (to write) the essay. 5. I (to watch) the football game on TV at 8 o'clock last night.
6. We (to play) chess when the lights (to go out).
7. Natalie (to fly) her kite while her sister (to ride) her bicycle.

2 года назад

Предмет: Английский язык, автор: Lss2003

Раскройте скобки, употребляя глаголы в Past Simple, Past Progressive или Past Prefect:
1. He had been doing his lessons by five o’clock and at five he was playing football in the yard. 2. Mark (be) at home when you (arrive)? – No, he (go) to school. 3. My parents (come) home by seven o’clock and at eight we (have) dinner. 4. His father (look) tired as he (work) hard before. 5. By seven o’clock I (learn) the poem and at eight o’clock I (watch) TV. 6. When he (see) me, I (read) the newspaper which I (buy) in the street. 7. Betty just (come) home when we (phone) her. 8. When Alison (enter) the room she (see) her son (play) with a ball which she (buy) in the shop. 9. They (arrive) to the theatre late. The play already (begin). 10. When I (come) into her room, she (play) the piano which her father (buy). 11. He (want) impress her parents as he (not meet) them before. 12. Mother (tell) us that she (plan) soup fish and a chocolate mousse for dinner. 13. His brother (be) taken to the hospital because he (have) an accident. 14. When we (arrive), mother (go) into the kitchen to do the last preparations for the meal. 15. Mary (bring) him a glass of water as he (ask) her about it. 16. When David (enter) the kitchen, he (see) that his cat (eat) meat.17. Jenny (tell) her mother, that she (water) the flowers. 18. We (want) to know which way they (choose). 19. She (be) afraid that they (not tell) the police the truth. 20. They (know) that he already (start) his work for our firm.

2 года назад

Предмет: Химия, автор: mazeratti2002

какой объём водорода образуется при взаимодействии 90 г цинка, содержащего 10% примесей, с соляной кислотой

8 лет назад

Предмет: Английский язык, автор: 87763706080

помогите пожалуйста надо! Английский язык

8 лет назад