The question is attached above. Please send step by step complete solution. I also request you please do not send any web link to this question because I am unable to  open the link every time  .

Asked by sudhanshubhushanroy | 14th Dec, 2017, 06:47: AM

Expert Answer:

begin mathsize 16px style cosxcos 2 xcos 3 straight x equals 1 fourth
4 cosxcos 2 xcos 3 straight x equals 1
2 open parentheses cosxcos 3 straight x close parentheses cos 2 straight x equals 1
2 open parentheses cos 4 straight x plus cos 2 straight x close parentheses cos 2 straight x equals 1
2 open parentheses 2 cos squared 2 straight x minus 1 plus cos 2 straight x close parentheses cos 2 straight x equals 1
4 cos cubed 2 straight x minus 2 cos 2 straight x plus 2 cos squared 2 straight x equals 1
simplifying space we space get
cos 4 straight x left parenthesis 2 cos 2 straight x plus 1 right parenthesis equals 0
cos 4 straight x equals 0 space rightwards double arrow 4 straight x equals open parentheses 2 straight n plus 1 close parentheses straight pi over 2 rightwards double arrow straight x equals open parentheses 2 straight n plus 1 close parentheses straight pi over 8 equals straight pi over 8 comma fraction numerator 3 straight pi over denominator 8 end fraction comma fraction numerator 5 straight pi over denominator 8 end fraction comma fraction numerator 7 straight pi over denominator 8 end fraction
cos 2 straight x equals fraction numerator negative 1 over denominator 2 end fraction rightwards double arrow straight x equals straight pi over 3 comma fraction numerator 2 straight pi over denominator 3 end fraction
There space are space 6 space solutions


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Answered by Sneha shidid | 15th Dec, 2017, 10:04: AM