phase( t, period, t0 )
t0
corresponds to phase zero.
For positive period, the returned value is in the range [0,1).
t
(floating point)period
(floating point)t0
(floating point)phase(5003,100,0) = 0.03
phase(5003,100,2) = 0.01
phase(5003,100,4) = 0.99
double phase(double, double, double)