Question

1+cosx=2sin^2x
Is there an identity I could substitute for?

Answer 1

do you know an identity for sin^2(x) that might be useful?
check out the half identities under the half-angle identities http://www.purplemath.com/modules/idents.htm

Answer 2

oh wait
are you solving an equation

Answer 3

or showing this is an identity or trying to show it isn't an identity

Answer 4

if this an equation you are solving just use sin^2(x)=1-cos^2(x)

Answer 5

Solving the equation

Answer 6

then write everything on one side and realize you have a quadratic in terms of cosine

Answer 7

do you see that or not see this so far?

Answer 8

\[\text{ Replace } sin^2(x) \text{ with } 1-cos^2(x) \\ 1+cos(x)=2(1-cos^2(x)) \\ \text{ put everything on one side } \\ 1+cos(x)-2(1-cos^2(x))=0 \\ \text{ distribute a little } \]

Answer 9

I don't see that

Answer 10

you don't see what?

Answer 11

the highest power is 2 and all the bases are cos(x)

Answer 12

so you have a quadratic in terms of cos

Answer 13

replace cos(x) with u
might make it easier for you to see

Answer 14

\[1+u-2(1-u^2)=0\]

Answer 15

Oh okay then. I see what you're saying.