Question

cos^2(2x)+cos^2(x)=1 -π<=x<=π/3

Answer 1

what did you do so far?

Answer 2

Hint \(cos(2x)=cos^2x-sin^2x\)

Answer 3

but what i need to do with the ^2?

Answer 4

better, cos(2x)= 2 cos^2(x) - 1

and square that

Answer 5

\((cos^2x-sin^2x)^2=(2cos^2x-1)^2\)

Answer 6

that distribution you did was incorrect! you know? it is not con^4x-sin^4x

Answer 7

\((a-b)^2=a^2-\color{magenta}{2ab}+b^2\)
you forgot the term in the middle

Answer 8

Yea i deleted this..
but its not cos2x, its cos^2(2x).. so wahat i need to do now?

Answer 9

But anyways use the \(2cos^2x-1\)

Answer 10

what*

Answer 11

square that \(cos^2(2x)=(2cos^2x-1)^2\)

Answer 12

you got it ?

Answer 13

oaa ok... thx :) let me try

Answer 14

okay

Answer 15

so now i got this.. how i continue?