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
2 cos^2 x
on the left
2 cos^2 x = cos x
cos x = 1/2
x = 60 degrees or pi/3 radians
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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