If sin x + sin²x = 1, thecos^8x+ 2 cos^6x + cos^4x:(1) 0(2) -1(4) I(3 – InterviewSolution

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1.	If sin x + sin²x = 1, thecos^8x+ 2 cos^6x + cos^4x:(1) 0(2) -1(4) I(3) 2
Answer» Sinx +sin²x=1sinx=1-sin²xsinx=cos²xsin²x=cos⁴xso,cos^8x+2cos^6x+cos⁴x=cos⁴x(cos⁴x+2cos²x+1)=sin²x (sin²x+2sinx+1)=sin⁴x+2sin³x+sin²x=sin⁴x+sin³x+sin³x+sin²x=sin²x(sin²x+sinx)+ sinx(sin²x+sinx)=sin²x×(1)+ sinx(1)=sin²x+sinx= 1

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