Вычислить: arccos (-корень из 3 /2 ) + arctg(корень из 3) - №19097595

Вычислить: arccos (-корень из 3 /2 ) + arctg(корень из 3)
- Предмет:
  Алгебра
- Автор:
  asherandrews
- 6 лет назад

Ответы 1

Arccos(-корень из 3/2) = 5п/6Arctg(корень из 3) = 2п/65п/6 + 2п/6 = 7п/6Ответ: 7п/6
- Автор:
  kasey
- 6 лет назад
- 0
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THE PERIODIC TABLE OF D.I.MENDELEYEV
There are certain natural groupings among the chemical elements in which every element is closely related to 1 the other elements in its group. In order to understand better these groupings, chemists have tried to fit the elements into a single plan.
One of the earlier attempts to fit the relationships 2 among the elements into a single law was made by John Ncwlands in England, who suggested the Law of Octaves.
This concept of the periodic repetition of properties was further developed by a Russian chemist Dmitri Mendeleyev who created a Periodic Table in which he arranged the elements according to their atomic weights and corresponding chemical properties.
D.I. Mendeleyev listed the elements known at the time (1869) in the order of their atomic weights from the lightest to the heaviest. The elements were arranged in a table ot eight columns; elements having similar properties appeared in the same columns or groups in the table. Mendeleyev even predicted that there were undiscovered elements and left empty spaces3 in this table for the new discoveries.
There are many ways the Periodic Table can be used. The table can be used to find the atomic number.
The atomic weight is also indicated in the table. The orbital arrangement of electrons 4 is shown for each of the elements. The common oxidation states are given. For most elements these numbers are the same 5 as the valence numbers.The table enables us to recognize 6 families of elements. For example, copper (29), silver (47), and gold (79) will all be found in the same column.
They have similar properties and are considered a chemical family. And at last 7 the table can be used to predict the properties of the elements. The fact that the Periodic Table can assist in predicting properties of elements has helped in the discovery of missing elements 8.

Ответить на вопросы по тексту
Who developed the concept of the periodic repetition of properties?
What columns are there in the Periodic Table?
What did Mendeleyev predict?
What certain natural groupings are there among the chemical elements?
What have chemists tried to do in order to understand better these groupings?
Who made one of the first attempts to fit the relationships among the elements?

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is closely related to
to fit the relationships
empty space
the orbital arrangement of electrons
the same
missing elements
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