Pre Calculus Repost Please Help
posted by Anonymous
Can someone help me solve this problem:
cos^2x + 5cosx  2= 0
I am having some trouble finding x

Reiny
treat it as a quadratic equation where
cosx = (5 ± √(25  4(1)(2))/2
= .37228 or 5.37..
The second answer lies beyond the range of the cosine function so
cosx = .37228 and x must be in the first or fourth quadrant.
x = 68.14 degrees or 291.86 degrees.
in radians it would be x = 1.18933 or 5.09385
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