Im not saying its right but I got <span>0,<span><span>2π</span>3</span>,<span><span>4π</span>3</span>,and2π </span><span><span>f<span>(x)</span></span>=2<span><span>cos2</span>x</span>−<span>cosx</span>−1=0</span>
Solve this quadratic equation for cos x.
Since a + b + c = 0, use shortcut.
One real root is cos x = 1 and the other is <span><span>cosx</span>=<span>ca</span>=−<span>12</span></span>.
Trig table and unit circle -->
a. cos x = 1 --> arc x = 0, and arc <span>x=2π</span>
b. <span><span>cosx</span>=−<span>12</span></span> --> arc <span>x=±<span><span>2π</span>3</span></span>
The arc <span><span>−2π</span>3</span> is co-terminal to the arc: <span><span>4π</span>3</span>
Answers for <span><span>(0,2π)</span>:</span> <span>0,<span><span>2π</span>3</span>,<span><span>4π</span>3</span>,and2<span>π</span></span>
