Find a sine function with these properties

amplitude 8
period 5
phase shift +pi

is the answer f(x) = 8sin(2pi/5(x-pi)) and f(x) = -8sin(2pi/5(x-pi)) or just the first one? If it's only the first one why so?

f(x) = 8sin(2pi/5(x-pi)) is the answer.
f(x) = -8sin(2pi/5(x-pi)) doesn't satisfy phase shift + pi.

I don't see why you multiplied by 2pi

f(x) = 8 * sin((x - pi) / 5)

is identical.

Also, it wouldn't be -8 * sin((x - pi) / 5) because (and I know this sounds a little weird) the amplitude is positive, not negative. The reasoning is that the amplitude is in relation to original f(x) = sin(x) graph


EDIT: You're right. f(x) = 8 * sin(2pi * (x - pi) / 5) is correct.