InterviewSolution
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InterviewSolution
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The general solution of `4 sin^4 x + cos^4x= 1` isA. `n pi pm alpha//2, alpha=cos^(-1) (1//5), AA n in Z`B. `n pi pm alpha//2, alpha=cos^(-1) (3//5), AA n in Z`C. `2 n pi pm alpha//2, alpha=cos^(-1) (1//3), AA n in Z`D. none of these |
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Answer» Correct Answer - A `4 sin^(4) x+cos^(4) x=1` `rArr (2 sin^(2) x)^(2) +1/4 (2 cos^(2) x)^(2)=1` or `(1-cos 2x)^(2) +1/4 (1+ cos 2x)^(2)=1` or `5 cos^(2) 2x-6 cos 2x+1=0` or `(cos 2x-1)(5 cos 2x-1)=0` or `cos 2x=1 or cos 2x=1/5` `rArr 2x=2npi or 2x=2npi pm alpha`, where `alpha=cos^(-1) (1/5), AA n in Z` |
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