# 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).