Question

- Solve 2cos (3x) - 1 = 0 on the interval [0, 21).T 77 97 151 177 23T12' 12' 12' 12 12'12T7T4' 4No solutionT 137 251 111 231 35718' 18 18 '18 18 1899

Answer 1

Let's solve the trig equation >>>

`\begin{gathered} \sqrt[]{2}\cos (3x)-1=0 \\ \sqrt[]{2}\cos (3x)=1 \\ \cos (3x)=\frac{1}{\sqrt[]{2}} \\ 3x=(\pi)/(4),(7\pi)/(4) \\ x=(\pi)/(12),(7\pi)/(12) \end{gathered}`

To get the other angles within 2π, we add 2π to these two angles. Thus,