## Precalculus (6th Edition) Blitzer

$0.6847,2.4569,3.8263,5.5985$
Step 1. Solve the equation to get $cos(x)=\pm\sqrt {\frac{3}{5}}=\pm0.7746$ Step 2. Find the reference angle as $x=cos^{-1}(0.7746)\approx0.6847$ Step 3. For $cos(x)= 0.7746$, we have solutions in $[0,2\pi)$ as $x=0.6847$ and $x=2\pi-0.6847\approx5.5985$ Step 4. For $cos(x)= -0.7746$, we have solutions in $[0,2\pi)$ as $x=\pi-0.6847\approx2.4569$ and $x=\pi+0.6847\approx3.8263$ Step 5. Thus, we have all the solutions in $[0,2\pi)$ as $x=0.6847,2.4569,3.8263,5.5985$