Remember that f(x) = A f(Bx-C) +D
Where |A| is the Amplitude and C/B is the phase Shift
Options
A, B C all have amplitudes of |3| so we have just eliminated D with the amplitude
We need a phase shift of C/B = pi/2
A has Pi/2
B has -Pi/2
C has pi/2 /2 = pi/4
Choice A -3 cos ( 2x-pi) +4 has a magnitude of 3 and and phase shift of pi/2
