Question Number 148445 by mathdanisur last updated on 28/Jul/21

if cos𝛂 = (√a) find 5 - 6cos2𝛂 + cos4𝛂 = ?

Commented bymathdanisur last updated on 28/Jul/21

Thank you Ser But, =(√𝛂) (alfa no) =(√a)

Commented bymathdanisur last updated on 28/Jul/21

answer: a)8a^2 -20a+12 b)8a^2 +18a-12 c)2a-1 d)8a^2 -8a+1 e)1-5a

Commented byOlaf_Thorendsen last updated on 28/Jul/21

you are right ! sorry mister. my eyes are very old.

Answered by Olaf_Thorendsen last updated on 28/Jul/21

x = 5−6cos2α+cos4α x = 5−6cos2α+2cos^2 2α−1 x = 2cos^2 2α−6cos2α+4 x = 2(2cos^2 α−1)^2 −6(2cos^2 α−1)+4 x = 2(2a−1)^2 −6(2a−1)+4 x = 8a^2 −20a+12

Commented bymathdanisur last updated on 28/Jul/21

Thank you very much Sir