To change P(t) open the Code and modify x(t), y(t), z(t)
You can use NE, PI, -NE, -PI, 2PI, -2PI as a or b (NE: e, PI: π)

Save by clickinghere(with the right mouse button) the file on your computer (change the name if you want, but leave ".htm").
At this point you can use it to calculate any lenght. Just open the source code, edit x(t), y(t), z(t), and run "save". You can repeat this several times.

Functions:
abs(a) / |a| log(a) / log of a base e
acos(a) / arc cosine of a max(a,b)
asin(a) / arc sine of a min(a,b)
atan(a) / arc tangent of a pow(a,b) / a to the power b
atan2(a,b) / arc tangent of a/b random() / random n. in [0,1)
ceil(a) / integer closest to a not < a round(a) / integer closest to a
cos(a) / cosine of a sin(a) / sine of a
exp(a) / exponential of a sqrt(a) / square root of a
floor(a) / integer closest to a not > a tan(a) / tangent of a
PI / π