Вопрос школьника по предмету Алгебра
Докажите тождество:
sina+cosa=√2cos(a-π/4)
Ответ учителя по предмету Алгебра
Используем формулу cos(x-y) = cosx*cosy+sinx*siny
sinα+cosα = √2cos(α-π/4) = √2*(cosα*cos(π/4)+sinα*sin(π/4)) = √2*(cosα*(√2/2)+sinα*(√2/2)) = √2*(√2/2)(cosα+sinα) = cosα+sinα
Похожие вопросы от пользователей
а) 1/5+1/2=7/10; б) 1/5+1/2=2/7;
в) 1/5+1/5=1/10; г) 1/5+1/2=2/10.
Помогите мне пожалуйста)))
Какое число надо прибавить к числителю и знаменателю дроби 11/41,чтобы она стала равной 1/3?
И еще решите вот этот пример)
32/35-14/7
Заранее спасибо!
Ответьте на вопросы по тексту.
Keep the Beauty of Russia.
Russia is a large country with many wonderful places. It stretches from the shores of the Pacific Ocean in Asia to the Baltic Sea in Europe, and from the cold, snowy Arctic to the sunny Black Sea coast.
Russia has nearly every kind of weather. Also it has many kinds of land rocky mointains, dry empty steppes, powerful rivers, wide plains and great forests and lands of endless winter. There are places of great beauty and places of historic interest The wil areas in the country are the home of many birds and animals It is for portant not to destroy these places but to keep them as they are everyone to enjoy.
Russia, like many other countries, has a system of national parks. The first national park, Losinyi Ostrov (Elk Sle) appeared in 1983. It is situated to the northeast of Moscow and a part of it in fact lies on the territory of the city. Now the park has become a popular place to visit for grown-ups and children especially schoolchil- dren who come to the park in big groups. The park has two visitor’s centres. The scientists who work in the park are interested in the flora and fauna this area.
Here are some unusual species of grasses and wild flowers that you can’t see so often any more, for example, different bluebells and lilies- of-the-valley. Most of the park’s territory is un der forests, and the common trees here are pines and firs.
As for the animals, there are about 300 species of them, mostly birds. They are forest birds and water birds like ducks and geese and even gulls. Here a visitor can see mice, squirrels, foxes, hares, otters, wild boars, deer and elks which gave the name to the park. There are not so many elks living in the park now, only 20 or 30, but the scientists hope to see more of these beautiful and strong animals in the park in the future.
Вопросы:
1) What territory does Russia take?
2) What type of land can you see on its territory?
3) Where are the lands of «endless winter»?
4) Why do people want to keep some places as they are?
5) How old is the first Russian national park?
6) Is the park a scientific centre as well as a place of great beauty?
7) Who visits this park?
8) What species of plants, birds and animals are common on the territory of the park?
9) What animal gave the name to the park? What is this animal like?