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Sonam Ghatode Grade:
        


cos nA= cosnA(1-nC2 tan2A-nC4 tan3A -…)


6 years ago

Answers : (1)

Badiuddin askIITians.ismu Expert
147 Points
										

Dear Sonam


we know 


cosnA + iSin nA =(cosA +isinA)n


open bracket with the help of binomial


cosnA + iSin nA =(cosA +isinA)n = cosnA + nC1 cosn-1A(isinA) + nC2cosn-2A(isinA)2 +.......


                             = (cosnA  - nC2cosn-2A(sinA)2 +.... ) + i(nC1 cosn-1A(sinA) - nC3 cosn-3A(sinA)3 .......)


 


compair Real  part


 Cos nA = (cosnA  - nC2cosn-2A(sinA)2 +.... )


              =cosnA(1-nC2 tan2A-nC4 tan3A -…)


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Badiuddin



6 years ago
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