ODE Toolkit recognizes the following pre-defined functions:

Trigonometric functions

sin(x) sine of x radians
cos(x) cosine of x radians
tan(x) tangent of x radians
cot(x) cotangent of x radians
asin(x) inverse sine (in radians) of x
acos(x) inverse cosine (in radians) of x
atan(x) inverse tangent (in radians) of x

Hyperbolic trig. functions:

cosh(x) hyperbolic cosine of x
sinh(x) hyperbolic sine of x
tanh(x) hyperbolic tangent of x
acosh(x) inverse hyperbolic cosine of x
asinh(x) inverse hyperbolic sine of x

Exponential and logarithmic functions:

exp(x) the value of e (the base of the natural logarithms) raised to the power of x
ln(x) natural logarithm of x
log(x) base-10 logarithm of x
pow(x, y) x raised to the power of y
sqrt(x) square root of x

Miscellaneous functions:

abs(x) absolute value of x
fact(x) or factorial(x) factorial of the greatest integer less than or equal to

Engineering functions:

sqp(t, l) square pulse of length l at time t
sqw(t, d, p) square wave of period p with duty cycle d% at time t
stair(t, l) stair function at time t with length l
step(t) step function at time t (0 if t < 0, 1 otherwise)
swp(t, l) sawtooth pulse at time t with length l
sww(t, d, p) sawtooth wave with duty cycle d% and period p at time t
trp(t, l) triangle wave pulse at time t with length l
trw(t, d, p) triangle wave at time t with duty cycle d% and period p