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) = 0.03phase(5003,100,2) = 0.01phase(5003,100,4) = 0.99double phase(double, double, double)