(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

18cos^2x+3cosx-1=0

it's a quadratic equation whose solutions are x= 1.4033+-2npi and x=1.9106+-2npi

2. Relevant equations

3. 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.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: 18cos^2x+3cosx-1 = 0

**Physics Forums | Science Articles, Homework Help, Discussion**