Common mathematical functions of C language and its usage

Transferred from: http://blog.sina.com.cn/s/blog_8b5a0d0001011779.html

Trigonometric functions: (All parameters must be radians)

1.acos

function declaration: ACOs (double x);
Purpose: Used to return the inverse cosine function of a given X.

2.asin

Function declaration: ASIN (double x);
Purpose: Used to return the inverse sine function of a given X.

3.atan

function declaration: Atan (double x);
Purpose: Used to return the inverse tangent function of a given X.

4.sin

function declaration: Sin (double x);
Purpose: Used to return the sine value of the given X.

5.cos

function declaration: Cos (double x);
Purpose: Used to return the cosine of a given X.

6.tan

function declaration: Tan (double x);
Purpose: Used to return the tangent of a given X.

7.atan2

function declaration: atan2 (double y, double x);
Purpose: Returns the inverse tangent value of the given X and Y coordinate values

Other functions:

8.atof

Function Name: atof (const char *s);
Function: Converts a string to a floating-point number
Usage: Double atof (const char *nptr);
program Example:
#i nclude <stdlib.h>
#i nclude <stdio.h>

int main (void)
{

Float arg,*point=&arg;
float F;
Char *str = "12345.67";

f = atof (str);
printf ("string =%s float =%f\n", str, f);
return 0;
}

9. Ceil and Floor

Function Name: Ceil
Floor
Functions: Rounding up
Rounding down
Usage: Double ceil (double x);
Double floor (double x);
program Example:

#i nclude<math.h>

int main (void)
{
Double number = 123.54;
Double Down, up;

Down = floor (number);
up = ceil (number);

printf ("Original number%5.2lf\n", number);
printf ("Number rounded down%5.2lf\n", down);
printf ("Number rounded up%5.2lf\n", up);

return 0;
The program runs the result: original number 123.54
Number rounded down 123.00
Number rounded up 124.00

10.fabs

Function Name: fabs
Function: Find the absolute value of the floating-point number x.
Usage: fabs (double x);

11.fmod

Function Name: Fmod
Function: Calculates the X-to-y modulus, which is the remainder
Usage: Double fmod (Double x, double y);
program Example:

#i nclude <stdio.h>
#i nclude <math.h>

int main (void)
{
Double x = 5.0, y = 2.0;
Double result;

result = Fmod (x, y);
printf ("The remainder of (%LF/%LF) is \
%lf\n ", x, y, result);
return 0;
}

12.abs

Function Name: ABS
Function: Returns the absolute value of the integer number.
Usage: Abs (number)
The number parameter can be any valid numeric expression. Returns NULL if number contains NULL, or 0 if the variable is uninitialized.

Power Index:

13.exp

Function Name: EXP
Function: Returns the n power of E.
Usage: exp (double x);

14.frexp

Function Name: frexp
function: To decompose a double-precision number into the exponent of the mantissa
Usage: Double frexp (double value, int *eptr);
program Example:

#i nclude <math.h>
#i nclude <stdio.h>

int main (void)
{
Double mantissa, number;
int exponent;
Number = 8.0;
Mantissa = frexp (number, &exponent);
printf ("The number%LF is", number);
printf ("%lf Times to the", mantissa);
printf ("Power of%d\n", exponent);
return 0;
}

15.log

Function Name: Log
Function: Natural logarithmic function ln (x)
Usage: Double log (double x);
program Example:

#i nclude <math.h>
#i nclude <stdio.h>
int main (void)
{
Double result;
Double x = 8.6872;
result = log (x);
printf ("The natural log of%LF is%lf\n", x, result);
return 0;
}

Log (x, y) =ln (y)/ln (x)

16.ldexp

Function Name: Ldexp
Function: Calculates value* (exp power of 2).
Usage: Double ldexp (double value, int exp);
program Example:
#i nclude
#i nclude
int main (void)
{
Double value;
Double x = 2;

Value = Ldexp (x,3);
printf ("The Ldexp value is:%lf\n", value);
return 0;
The result of the operation is: 2*2^3=16.

17.log10

Function Name: log10
Function: Returns the base 10 logarithm.
Usage: log10 (double x);

18.sqrt

Function Name: sqrt
Function: Returns the square root of the specified number.
Usage: sqrt (double x);

19.modf

Function Name: MODF
function: Divide the number into exponent and mantissa
Usage: Double modf (Double value, double *iptr);
program Example:
#i nclude <math.h>
#i nclude <stdio.h>
int main (void)
{
Double fraction, Integer;
Double number = 100000.567;
fraction = MODF (number, &integer);
printf ("The whole and fractional parts of%LF is%lf and%lf\n", number, integer, fraction);
return 0;
}

20.pow

Name of function: POW
Function: Returns the specified number of times the specified power.
Usage: POW (double x, double y);(will return the Y power of X)

Hyperbolic functions:

21.cosh

Function Name: cosh
Function: Returns the hyperbolic cosine of the specified angle.
Usage: Double Cosh (double x (measured in radians));

22.sinh

Function Name: Sinh
Function: Returns the hyperbolic sine value of the specified angle.
Usage: Sinh (double x);(where parameter x must be Radian)

23.tanh

Function Name: Tanh
Function: Returns the hyperbolic tangent value of the specified angle.
Usage: Tanh (double x);

Common mathematical functions of C language and its usage