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To Prove:

sinx/cos3x + sin3x/cos9x + sin9x/cos27x  =1/2sin26x/(cosxcox27x)

6 years ago


Answers : (3)


Dear Nehal Wani

sinx/cos3x + sin3x/cos9x + sin9x/cos27x  

or sin2x/2cos3xcosx + sin6x/2cos9xcos3x + sin18x/2cos27xsin18x

or  sin(3x-x)/2cos3xcosx + sin(9x-3x)/2cos9xcos3x + sin(27x-9x)/2cos27xsin18x

or 1/2 [tan3x -tanx  + tan9x -tan3x + tan27x-tan9x]

or  1/2 [tan27x-tanx]


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