Is the Phase Constant in SHM Conceptually Significant?

[alingy1]

Please look at picture.
My textbook only gives the answer with -pi as a phase constant. But, since we are at "a switching point" on the unit circle, the sign doesn't really matter. The graphs give the same result whether a positive or negative sign is used. Am I right? Does it conceptually change anything?

 

[berkeman]

Please look at picture.
My textbook only gives the answer with -pi as a phase constant. But, since we are at "a switching point" on the unit circle, the sign doesn't really matter. The graphs give the same result whether a positive or negative sign is used. Am I right? Does it conceptually change anything?

I'm guessing that pi is the constant. Can you show us the equation?

When you have y(t) = sin (ωt - Θ), Theta is the phase constant...