paulo1913 Posted April 9, 2009 Posted April 9, 2009 How do I prove that: (cosx-cos3x)/(sin3x-sinx)= tan2x?
WhataBohr Posted April 14, 2009 Posted April 14, 2009 How do I prove that: (cosx-cos3x)/(sin3x-sinx)= tan2x? do you want the proof?
John Cuthber Posted April 16, 2009 Posted April 16, 2009 He may well want it but it's not this sites habit to give the answer. Giving hints and advice is better for th estudent.
WhataBohr Posted April 17, 2009 Posted April 17, 2009 use the following identites sin2x = 2sinxcosx cos2x = 1-2sin^2x cos3x = 4cos^3x - 3cosx sin3x = 3sinx -4sin^3x - sinx i did the proof its actually pretty simple.. good luck
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