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

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