# trig

Prove the identity. (must work with left side)

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

1. 👍 0
2. 👎 0
3. 👁 47
1. Let x^2 = y
What you have written is equivalent to
1 - 2 sin y = cos y
which is not a correct identity.

It looks like you have put parentheses in the wrong places. The outside ones are unecessary.

A correct version would be
1 - 2 (sin x)^2 = cos 2x
That is one of the double-angle identities

1. 👍 0
2. 👎 0
posted by drwls

## Similar Questions

1. ### math

Prove the identity: cos^4(x)-sin^4(x)=1-2sin^2(x).with explanation im confused on this one cause of the 4th power of the sine. does this mean that we put it in the calculator 4 times? and what exactly does it mean by prove the

asked by Anonymous on April 15, 2012
2. ### trig

it says to verify the following identity, working only on one side: cotx+tanx=cscx*secx Work the left side. cot x + tan x = cos x/sin x + sin x/cos x = (cos^2 x +sin^2x)/(sin x cos x) = 1/(sin x cos x) = 1/sin x * 1/cos x You're

asked by Devon on May 7, 2007
3. ### Math pre cal

prove the following identity cos^4X - sin^4X = 1-2sin^2X

asked by Breanna on September 28, 2009
4. ### Trigonometry

Prove the identity sin(x+y+z)+sin(x+y-z)+sin(x-y+z)+ sin(x-y-z) = 4 sin(x)cos(y)cos(z) This identity is so long and after i tried to expand the left side and it just looked something crap Thanks for you help :)

asked by Tommy on July 19, 2008
5. ### Trigonometry

I need to prove that the following is true. Thanks. csc^2(A/2)=2secA/secA-1 Right Side=(2/cosA)/(1/cosA - 1) = (2/cosA)/[(1-cosA)/cosA] =2/cosA x (cosA)/(1-cosA) =2/(1-cosA) now recall cos 2X = cos^2 X - sin^2 X and we could say

asked by Dirk on April 17, 2007
6. ### advanced function

pls. help: prove the identity sin2x+sin2y=2sin(x+y)cos(x-y)

asked by justme on November 29, 2011
7. ### Math

Prove each identity: a) 1-cos^2x=tan^2xcos^2x b) cos^2x + 2sin^2x-1 = sin^2x I also tried a question on my own: tan^2x = (1 – cos^2x)/cos^2x R.S.= sin^2x/cos^2x I know that the Pythagorean for that is sin^2x + cos^2x That's all

asked by Kate on July 18, 2011
8. ### Pre-Calculus

I don't understand,please be clear! Prove that each equation is an identity. I tried to do the problems, but I am stuck. 1. cos^4 t-sin^4 t=1-2sin^2 t 2. 1/cos s= csc^2 s - csc s cot s 3. (cos x/ sec x -1)- (cos x/ tan^2x)=cot^2 x

asked by Anonymous on October 31, 2013
9. ### math (trig)

Find sin(x/2) if sin(x)= -0.4 and 3pi/2 < or equal to (x) < or equal to 2pi Let's use cos 2A = 1 - 2sin2 A and we can match cos x = 1 - 2sin2 (x/2) so we will need cos x we know sin x = -.4 and x is in the fourth quadrant, so the

asked by aziiancaligirl on July 15, 2007
10. ### calc

Where do I start to prove this identity: sinx/cosx= 1-cos2x/sin2x please help!! Hint: Fractions are evil. Get rid of them. Well, cos2x = cos2x - sin2x, so 1-coscx = 1 - cos2x - sin2x = 1 - cos2x + sin2x You should be able to

asked by maria on October 21, 2006

More Similar Questions