Find a function of the form y=Asin(kx)\displaystyle {y}={A}{\sin{{\left({k}{x}\right)}}} or y=Acos(kx)\displaystyle {y}={A}{\cos{{\left({k}{x}\right)}}} whose graph matches the function shown below:

12345678-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20123-1-2-3

Leave your answer in exact form; if necessary, type pi for π\displaystyle \pi.

y=\displaystyle {y}=