# NMODL’s built-in functions

These functions, which are provided by the C language math library, can be called from within NMODL code. With the exception of abs(), all expect double-precision floating point arguments and return double-precision floating point values.

`acos(x)`

- compute the arc cosine- Returns the arc cosine of its argument (arccosx). The argument must be in the range -1.0 to 1.0.
`asin(x)`

- compute the arc sine- Returns the arc sine of its argument (arcsinx). The argument must be in the range -1.0 to 1.0.
`atan(x)`

- compute the arc tangent- Returns the arc tangent of its argument (arctanx).
`atan2(y,x)`

- compute the arc tangent of y/x- Returns the arc tangent of the ratio y/x (arctany/x).
`ceil(x)`

- round upwards- Returns the smallest integral value greater than or equal to its argument (x).
`cos(x)`

- compute the cosine- Returns the cosine of its argument (cosx). The angle is expressed in radians.
`cosh(x)`

- compute the hyperbolic cosine- Returns the hyperbolic cosine for a real argument (coshx).
`exp(x)`

- compute the exponential function- Returns the value of e raised to the argument power (ex).
`fabs(x)`

- compute the absolute value of a floating point number- Returns the absolute value of its argument (|x|).
`floor(x)`

- round downwards- Returns the largest integral value less than or equal to its argument (x).
`fmod(x,y)`

- compute x modulo y- Returns the value of x modulo y (x y), the remainder resulting from x/y.
`log(x)`

- compute the natural logarithm- Returns the natural logarithm of its argument (lnx).
`log10(x)`

- compute the base 10 logarithm- Returns the base 10 logarithm of its argument (log10 x).
`pow(x,y)`

- compute x raised to the y power- Returns the value of x raised to the power of y (x
^{y}). `sin(x)`

- compute the sine- Returns the sine of its argument (sinx). The angle is expressed in radians.
`sinh(x)`

- compute the hyperbolic sine- Returns the hyperbolic sine for a real argument (sinhx).
`sqrt(x)`

- compute the square root- Returns the positive square root of its argument (x).
`tan(x)`

- compute the tangent- Returns the tangent of its argument (tanx). The angle is expressed in radians.
`tanh(x)`

- compute the hyperbolic tangent- Returns the hyperbolic tangent for a real argument (tanhx).