- #1
solve
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Homework Statement
18cos^2x+3cosx-1=0
it's a quadratic equation whose solutions are x= 1.4033+-2npi and x=1.9106+-2npi
Homework Equations
The Attempt at a Solution
The answers to this problem are given as x= +-1.4033+-2npi and x=+-1.9106+-2npi
Why are x's both positive and negative?
Thanks.