Solution:
Give the following below
![\begin{gathered} amplitude=3 \\ period=(\pi)/(2) \\ midline,\text{ }y=-1 \\ Passing\text{ through the point }(0,2) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/7our4ma5feq76a81a5ignvrrvdj0rny141.png)
To find the cosine function, we will apply the general formula for cosine function below
![\begin{gathered} f(x)=a\cos(bx-c)+d \\ Where \\ a\text{ is the amplitude} \\ b\text{ represents the speed of the cycle} \\ d\text{ is the vertical shift} \\ (c)/(b)\text{ is the phase shift \lparen horizontal shift\rparen} \\ Period=(2\pi)/(b) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/rn3wz25rou4o9vkyt4yx17xfy1yxgx4zn7.png)
To find the value of b
![\begin{gathered} Period=(\pi)/(2) \\ (2\pi)/(b)=(\pi)/(2) \\ Crossmultiply \\ b*\pi=2*2\pi \\ b=(4\pi)/(\pi) \\ b=4 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/f1fvuyl4looyg7e99tpce0sxum5gv0sqha.png)
![\begin{gathered} a=3 \\ b=4 \\ d=-1 \\ c=0 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/nmvd12xllrrfpapaxnc3hve8x8rxe5rdch.png)
Substitute the values of the variables into the general formula for cosine function
![\begin{gathered} f(x)=a\cos(bx-c)+d \\ f(x)=3\cos(4x-0)-1 \\ f(x)=3\cos4x-1 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/ijpv5mbgov62reglu5tr03xggsjo30tv71.png)
Applying a graphing tool,
The graph of one cycle of the function is shown below