Предмет: Алгебра, автор: ритмик

помогите, пожалуйста:
2cos(2) x+cos х = 0

Ответы

Автор ответа: sangers1959
1
2(cos²x-sin²x)+cosx=0
2cos²x-2sin²x+cosx=0
2cos²x+2-2sin²x-2+cosx=0
2cos²x+2cos²x+cosx-2=0
4cos²x+cosx-2=0
cosx=v
4v²+v-2=0     
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Robert Fulton – Steamboat Inventor
By: Sue Peterson
Robert Fulton was born in Pennsylvania in 1765. He learned to read and write at home. Later, he was sent to a Quaker school for his education. Fulton showed an early interest in inventions and built a rocket for the Fourth of July when he was a teenager. Fulton enjoyed thinking about ideas for new inventions.

Fulton learned to draw as a child and excelled in art. When he finished his schooling, he worked in Philadelphia where he painted portraits and landscapes. At age 23, Fulton decided to move to England and while living there, he invented many different kinds of machines. He was very interested in how canal systems worked. Canals are deep paths of water for boats to travel through from one body of water to another. Usually they are man-made.

Fulton eventually moved to France and worked on canal systems. There, he used his talents for art and invention to design a submarine, which is a boat that can go underwater. Then he built a steamboat, a large boat that is powered by heating water to make steam which makes the paddlewheels move.

When Fulton moved back to the U.S., he took his steamboat invention and established the first steamboat service in the world on the Hudson River in New York. People paid money to travel by steamboat.

The first steamboat trip took 32 hours to cover 150 miles (240 kilometers) in 1807. That is equal to moving at about 5 miles (8 kilometers) an hour. That is as fast as a person can walk.

Robert Fulton is known as an American inventor who developed the first steamboat service to help people travel from one place to another. He is also called the “Father of Steam Navigation”.

Choose the right words to compete the sentences.

A steamboat is powered by ............................................
Robert was interested in .............................................
Robert's drawing were always ..............................
Запишите элементы на пустые поля сверху (каждый может быть использован несколько раз)
vapour.
man-made waterways.
exceptional.
a paddlewheel.
watercourses.
about machines.
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