pi = 3.141592653589793238462643
The constant equal to the ratio of the length of any circle to its diameter.
e = 2.718281828459045235360287
The constant equal to the base of natural logarithms.
t
Predefined variable denoting the current time value. Used with transient
problems.
x
Predefined variable denoting the Cartesian x-coordinate.
y
Predefined variable denoting the Cartesian y-coordinate.
r
Predefined variable denoting the polar r-coordinate.
phi
Predefined variable denoting the polar φ-coordinate in degrees.