C Standard Library:4 Mathematical Functions:

4 Mathematical Functions: <math.h>

The header <math.h> declares mathematical functions and macros.
The macros EDOM and ERANGE (found in <errno.h>) are non-zero integral constants that are
used to signal domain and range errors for the functions; HUGE_VAL is a positive double value.
A domain error occurs if an argument is outside the domain over which the function is
defined. On a domain error, errno is set to EDOM; the return value is implementation-defined.
A range error occurs if the result of the function cannot be represented as a double. If the

result overflows, the function returns HUGE_VAL with the right sign, and errno is set to
ERANGE. If the result underflows, the function returns zero; whether errno is set to ERANGE is
implementation-defined.
In the following table, x and y are of type double, n is an int, and all functions return double.
Angles for trigonometric functions are expressed in radians.
sin(x) sine of x
cos(x) cosine of x
tan(x) tangent of x
asin(x) sin^-1(x) in range [-pi/2,pi/2], x in [-1,1].
acos(x) cos^-1(x) in range [0,pi], x in [-1,1].
atan(x) tan^-1(x) in range [-pi/2,pi/2].
atan2(y,x) tan^-1(y/x) in range [-pi,pi].
sinh(x) hyperbolic sine of x
cosh(x) hyperbolic cosine of x
tanh(x) hyperbolic tangent of x
exp(x) exponential function e^x
log(x) natural logarithm ln(x), x>0.
log10(x) base 10 logarithm log₁₀(x), x>0.
pow(x,y) x^y. A domain error occurs if x=0 and y<=0, or if x<0 and y is not an integer.
sqrt(x) sqare root of x, x>=0.
ceil(x) smallest integer not less than x, as a double.
floor(x) largest integer not greater than x, as a double.
fabs(x) absolute value |x|
ldexp(x,n) x*2ⁿ
frexp(x, int*ip) splits x into a normalized fraction in the interval [1/2,1) which is returned, and a power of 2, which is stored in *exp. If x is zero, both parts of the result are zero.
modf(x, double*ip) splits x into integral and fractional parts, each with the same sign as x. It stores the integral part in *ip, and returns the fractional part.
fmod(x,y) floating-point remainder of x/y, with the same sign as x. If y is zero, the result is implementation-defined.