В треугольнике угол при одной из вершин равен 46°, внешний угол при другой вершине равен 127° Найдите третий угол.

решите уравнение х2-7х-4=0 и найдите сумму его корней

при помощи каких реакций можно осуществить следующие превращения:

Са ---СаН2 ---Са(ОН)2------СаSO3------CaO

    An American Thomas Edison made the first machine with moving pictures in 1891. It was called a kinetoscope. Then in 1895 a machine that projected pictures on to a screen was built by two French brothers, August and Louis Lumiere. They called their machine a cinematographe. The pictures from this machine were shown one after the other very quickly.

    The Lumiere brothers gave the world’s first film show in 1896, and in America the world’s first cinema was built in Pittsburgh in 1905.

     In the beginning films were made to show news, but by 1902 filmmakers began to write stories for film and use actors. These films were very popular in America, and Hollywood became important in the film-making industry. The first “talkie” (film and sound) was shown in America in 1927. It was called “The Jazz Singer”.

Луч SC является бесстекрисой угла АSB, а отрезки SA и SB равны. Докажите, что треугольник SAC= треугольнику SBC.