Explanation:
The function is given below as
[tex]y=4cos(18x)[/tex]
To sketch the graph, we will have the image below at the interval
[tex]0\leq x\leq40[/tex]
The periodicity of the model will be calculated below as
[tex]\begin{gathered} 18=\frac{2\pi}{B} \\ B=\frac{2\pi}{18} \\ B=\frac{\pi}{9} \\ B=\frac{180}{9} \\ B=20^0 \end{gathered}[/tex]
Hence,
The periodicity is
[tex]20^0[/tex]
