Косинус угла В вычисляем, используя теорему косинусов о том, что квадрат одной из сторон
треугольника равен разности суммы квадратов двух других сторон и удвоенного произведения
этих сторон на косинус угла между ними:
АС^2 = АВ^2 + ВС^2 - 2 АВ х ВС х косинус угла В.
косинус угла В = (АВ^2 + ВС^2 - АС^2)/2 АВ х ВС.
косинус угла В = (8^2 + 5^2 - 7^2)/ 2 х 8 х 5 =( 64 + 25 - 49)/80 = 1/2.
Ответ: косинус угла В = 1/2.
Автор:
hugo99Добавить свой ответ
Exercise 3. Read the text. Choose the right meaning for the italicized words in the sentences given below.
The largest country in the world, Russia offers a broad array of travel experiences. Historical sites and cultural activities in the country's great cities abound. Whether you're exploring the grounds of Moscow's Kremlin or wandering through the central part of Russia, your adventure is not soon forgotten.
One of the inspiring places is Kizhi Island which is located in Karelia, a region in Northwestern Russia that borders Finland and the White Sea. It is best known for its incredible open-air museum. The museum's collection features the 120-foot high Church of the Transfiguration of Our Savior, a structure made famous by its 22 domes. Other tourist attractions include dozens of wooden houses, windmills, chapels and barns.Another Russian tourist attraction is Suzdal, the jewel of Russia's "Golden Ring", one of the ancient cities that the country has preserved as living muscums of its cultural past. Here you can see the best Russia's historic architecture, onion-dome topped kremlins, cathedrals and monasteries. Founded in 1024, the city is like an open-air museum that transports visitors back in time.
1. The largest country in the world, Russia offers a broad array of
travel experiences.
a) a wide choice
b) an all-round presentation
c) a sound view
2. Cultural activitics in the country's great citics abound.
a) are presented in large numbers
b) are varied
c) are interesting
3. The museum's collection features the 120-foot high Church.
a) describes
b) includes someone as an important part
c) discusses or mentions something in a noticeable way
4. The country has preserved them as living museums of its cultural
past.
a) historic places where people live
b) places where museum pieces are living beings
c) museums which will never die
5. The city is like an open-air museum that transports visitors back in
time.
a) takes people to the past
b) makes people feel that they were in the past
c) show people out-of-date things
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