Let y=13cos[2(xπ4)]\displaystyle {y}={13}{\cos{{\left[{2}{\left({x}-{\frac{{\pi}}{{{4}}}}\right)}\right]}}}.

What is the amplitude?  

What is the period?  

What is the phase shift?  

[NOTE: If needed, you can enter π\displaystyle \pi as 'pi' in your answers.]