What is the equation of the graph below?

A coordinate plane. The graph starts and rises to (negative 360 comma 1). It starts to fall through (negative 270 comma 0) to (negative 180 comma negative 1). It then rises through (negative 90 comma 0) to (0 comma 1). It then falls through (90 comma 0) to (180 comma negative 1). It then rises through (270 comma 0) to (360 comma 1).
y = cosine (x + StartFraction pi Over 2 EndFraction)
y = cosine (x + 2 pi)
y = cosine (x + StartFraction pi Over 3 EndFraction)
y = cosine (x + pi)