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paulo1913

Trig Proof

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How do I prove that:

 

(cosx-cos3x)/(sin3x-sinx)= tan2x?

 

 

do you want the proof?

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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.

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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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