Предмет: Геометрия, автор: lenaOK

найти площадь правельного 12 угольника вписанного в окр-ть с радиусом R

Ответы

Автор ответа: ellagabdullina
0

1. 360 : 12 = 30 градусов - градусная мера одной дуги или величина соотвтствующего центрального угла.

Разобьем 12-ти угольник на 12 равнбедренных треугольников с углом 30 градусов и боковыми сторонами , равными R. Найдем площадь одного треугольника и умнжим на 12.

S = 1/2R*R *sin 30 = 1/2R^2 * 1/2 = 1/4R^2

площадь 12-ти угольника будет равна:

1/4R^2 * 12 = 3R^2

ответ: 3R^2

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1. А. Прочитайте текст и постарайтесь догадаться о значении выделенных слов.

Computers are now essential in many areas of life — modem

banking, information technology and many others. However, this

is not true for education.

There are some subjects which may be better taught using computers. Elementary mathematics, elementary language learning,

any subject that requires a student to memorize basic facts through

repetition (повторение) is good to computer learning. The computer can be programmed to provide an endless number of simple

questions, and as the student answers these questions the facts are

learned.

However, in the learning and practice of more complex ideas,

the computer is not adequate. A computer can evaluate (оценить)

an answer as right or wrong, but it cannot determine why. It cannot

find out why a student is making mistakes, and then explain important concepts in a different way so the student will understand. Task

connected with explanation cannot be taught by computers as there

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Thus, while computers may be useful for practising simple

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B. Подберите к каждому слову или словосочетанию в колонке А соответствующее из колонки В.

А В

1. essential а. thing that can vary

2. area of life b. idea, opinion

3. memorize с absolutely necessary

4. adequate d. most important

5. concept e. sphere of activity

6. variable f. learn by heart

7. indispensable g. satisfactory, sufficient

С Заполните пропуски антонимами и синонимами.

right ... ... new, up-to-date

... complex most important ...

adequate ... ... absolutely necessary
Предмет: Математика, автор: ilahe1601