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4 天前 · Viète. de Moivre. Euler. Fourier. v. t. e. In trigonometry, trigonometric identities are equalities that involve trigonometric functions and are true for every value of the occurring variables for which both sides of the equality are defined. Geometrically, these are identities involving certain functions of one or more angles.
3 天前 · Wireless LAN (WLAN) channels are frequently accessed using IEEE 802.11 protocols. The 802.11 standard provides several radio frequency bands for use in Wi-Fi communications, each divided into a multitude of channels numbered at 5 MHz spacing (except in the 45/60 GHz band, where they are 0.54/1.08/2.16 GHz apart) between the centre frequency of the channel.
3 天前 · This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for duplex, bidirectional traffic. They usually use port numbers that match the services of the corresponding TCP or UDP implementation, if they ...
3 天前 · The number π (/paɪ/; spelled out as "pi") is a mathematical constant that is the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. The number π appears in many formulae across mathematics and physics. It is an irrational number, meaning that it cannot be expressed exactly as a ratio of two integers, although ...
3 天前 · Russia,[b] or the Russian Federation,[c] is a country spanning Eastern Europe and North Asia. It is the largest country in the world by area, extending across eleven time zones and sharing land borders with fourteen countries.[d] It is the world's ninth-most populous country and Europe's most populous country. Russia is a highly urbanized ...
1 天前 · The Sun is the star at the center of the Solar System. It is a massive, nearly perfect ball of hot plasma,[18][19] heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies. It is by far the most important source of ...
2 天前 · Germany,[e] officially the Federal Republic of Germany,[f] is a country in the western region of Central Europe. It is the second-most populous country in Europe after Russia[g] and the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the south. Its 16 constituent ...
