document.write( "Question 1161865: Two frequencies of sound are played on an instrument governed by the function n(t)=8cos(20pie*t)cos(1000pie*t). What is the peroid and frequency of the fast and slow oscillation? What is ampmitude? \n" ); document.write( "
Algebra.Com's Answer #785497 by ikleyn(52779)\"\" \"About 
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document.write( "cos(a)*cos(b) = \"%281%2F2%29%2Acos%28a-b%29\" + \"%281%2F2%29%2Acos%28a%2Bb%29\".\r\n" );
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document.write( "There are two harmonic modes in this instrument.\r\n" );
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document.write( "The low frequency is \"%281000-20%29%2F2\" Hertz = 490 Hertz;  the period is  \"1%2F490\" of a second.\r\n" );
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document.write( "The high frequency is \"%281000%2B20%29%2F2\" Hertz = 510 Hertz;  the period is  \"1%2F510\" of a second.\r\n" );
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document.write( "The amplitude is 4 units for each harmonic mode.\r\n" );
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