Posted by **Haley** on Tuesday, November 20, 2012 at 3:21pm.

cos^2x-sin^2 x+1=cos x

- pre-calc help !!!!!!! -
**Damon**, Tuesday, November 20, 2012 at 3:33pm
sin^2 x = 1 - cos^2 x

so we have

cos^2 x - 1 + cos^2 x + 1

or

2 cos^2 x

on the left

so

2 cos^2 x = cos x

cos x = 1/2

x = 60 degrees or pi/3 radians

or

300 degrees or 5 pi/3 radians

- pre-calc help !!!!!!! -
**Reiny**, Tuesday, November 20, 2012 at 3:43pm
from Damon's middle section:

2cos^2 x - cosx = 0

cosx(2cosx - 1) = 0

cosx = 0 or cosx = 1/2

so from cosx=1/2 we have the 2 answers that Damon gave

from cosx = 0 , we also have

x = 90° or x = 270°

x = π/2 or x = 3π/2

## Answer This Question

## Related Questions

- pre-cal - Simplify the given expression........? (2sin2x)(cos6x) sin 2x and cos ...
- Calc. - Differentiate. y= (cos x)^x u= cos x du= -sin x dx ln y = ln(cos x)^x ln...
- TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...
- tigonometry - expres the following as sums and differences of sines or cosines ...
- Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...
- Math, Pre-Calc - the original problem was: Solve: sin(3x)-sin(x)=cos(2x) so far ...
- algebra - Can someone please help me do this problem? That would be great! ...
- trig - Reduce the following to the sine or cosine of one angle: (i) sin145*cos75...
- Math - Calculus - The identity below is significant because it relates 3 ...
- pre calc trig check my work please - sin x + cos x -------------- = ? sin x sin ...

More Related Questions