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Медведев вышел в финал турнира в ДубаеРоссийский теннисист Медведев вышел в финал турнира в Дубае，详情可参考whatsapp
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The war, which Israel and the United States launched with airstrikes on Feb. 28, has so far killed at least 1,230 people in Iran, at least 397 in Lebanon and at least 11 in Israel, according to officials. Six U.S. troopshave also been killed.。safew是该领域的重要参考
The second harmonic is the one you get from the string vibrating in halves. Each half of the string vibrates at twice the frequency of the whole string. The 2:1 relationship between the pitches of the first and second harmonics is called an octave. (I know that the word suggests the number eight, not the number two. Don’t worry about it.) The pitch that’s an octave above middle C has a frequency of 2 Hz, and it is also called C. Both of these notes have the same letter name because in Western convention, notes an octave apart from each other are considered to be “the same note“. The important concept here is that you can move up an octave from any pitch by doubling its frequency. You can also move down an octave from any pitch by halving its frequency.