C Library math.h Functions

The math.h header defines various C mathematical functions and one macro. All the functions available in this library take double as an argument and return double as the result. Let us discuss some important C math functions one by one.

C Math Functions

1. double ceil (double x)

The C library function double ceil (double x) returns the smallest integer value greater than or equal to x.

Syntax

double ceil(double x);

Example

C

// C code to illustrate
// the use of ceil function.
#include <math.h>
#include <stdio.h>

int main()
{
    float val1, val2, val3, val4;

    val1 = 1.6;
    val2 = 1.2;
    val3 = -2.8;
    val4 = -2.3;

    printf("value1 = %.1lf\n", ceil(val1));
    printf("value2 = %.1lf\n", ceil(val2));
    printf("value3 = %.1lf\n", ceil(val3));
    printf("value4 = %.1lf\n", ceil(val4));

    return (0);
}

Output

value1 = 2.0
value2 = 2.0
value3 = -2.0
value4 = -2.0

2. double floor(double x)

The C library function double floor(double x) returns the largest integer value less than or equal to x.

Syntax

double floor(double x);

Example

C

// C code to illustrate
// the use of floor function
#include <math.h>
#include <stdio.h>

int main()
{
    float val1, val2, val3, val4;

    val1 = 1.6;
    val2 = 1.2;
    val3 = -2.8;
    val4 = -2.3;

    printf("Value1 = %.1lf\n", floor(val1));
    printf("Value2 = %.1lf\n", floor(val2));
    printf("Value3 = %.1lf\n", floor(val3));
    printf("Value4 = %.1lf\n", floor(val4));

    return (0);
}

Output

Value1 = 1.0
Value2 = 1.0
Value3 = -3.0
Value4 = -3.0

3. double fabs(double x)

The C library function double fabs(double x) returns the absolute value of x.

Syntax

syntax : double fabs(double x)

Example

C

// C code to illustrate
// the use of fabs function
#include <math.h>
#include <stdio.h>

int main()
{
    int a, b;
    a = 1234;
    b = -344;

    printf("The absolute value of %d is %lf\n", a, fabs(a));
    printf("The absolute value of %d is %lf\n", b, fabs(b));

    return (0);
}

Output

The absolute value of 1234 is 1234.000000
The absolute value of -344 is 344.000000

4. double log(double x)

The C library function double log(double x) returns the natural logarithm (base-e logarithm) of x. 

Syntax

double log(double x)

Example

C

// C code to illustrate
// the use of log function

#include <math.h>
#include <stdio.h>

int main()
{
    double x, ret;
    x = 2.7;

    /* finding log(2.7) */
    ret = log(x);
    printf("log(%lf) = %lf", x, ret);

    return (0);
}

Output

log(2.700000) = 0.993252

5. double log10(double x)

The C library function double log10(double x) returns the common logarithm (base-10 logarithm) of x. 

Syntax

double log10(double x);

Example

C

// C code to illustrate
// the use of log10 function
#include <math.h>
#include <stdio.h>

int main()
{
    double x, ret;
    x = 10000;

    /* finding value of log1010000 */
    ret = log10(x);
    printf("log10(%lf) = %lf\n", x, ret);

    return (0);
}

Output

log10(10000.000000) = 4.000000

6. double fmod(double x, double y)

The C library function double fmod(double x, double y) returns the remainder of x divided by y. 

Syntax

double fmod(double x, double y) 

Example

C

// C code to illustrate
// the use of fmod function
#include <math.h>
#include <stdio.h>

int main()
{
    float a, b;
    int c;
    a = 8.2;
    b = 5.7;
    c = 3;
    printf("Remainder of %f / %d is %lf\n", a, c,
           fmod(a, c));
    printf("Remainder of %f / %f is %lf\n", a, b,
           fmod(a, b));

    return (0);
}

Output 

Remainder of 8.200000 / 3 is 2.200000
Remainder of 8.200000 / 5.700000 is 2.500000

7. double sqrt(double x)

The C library function double sqrt(double x) returns the square root of x. 

Syntax

double sqrt(double x);

Example

C

// C code to illustrate
// the use of sqrt function
#include <math.h>
#include <stdio.h>

int main()
{

    printf("Square root of %lf is %lf\n", 225.0,
           sqrt(225.0));
    printf("Square root of %lf is %lf\n", 300.0,
           sqrt(300.0));

    return (0);
}

Output

Square root of 225.000000 is 15.000000
Square root of 300.000000 is 17.320508

8. double pow(double x, double y)

The C library function double pow(double x, double y) returns x raised to the power of y i.e. xy.

Syntax

double pow(double x, double y);

Example

C

// C code to illustrate
// the use of pow function
#include <math.h>
#include <stdio.h>

int main()
{
    printf("Value 8.0 ^ 3 = %lf\n", pow(8.0, 3));

    printf("Value 3.05 ^ 1.98 = %lf", pow(3.05, 1.98));

    return (0);
}

Output

Value 8.0 ^ 3 = 512.000000
Value 3.05 ^ 1.98 = 9.097324

9. double modf(double x, double *integer)

The C library function double modf(double x, double *integer) returns the fraction component (part after the decimal), and sets integer to the integer component.

Syntax

double modf(double x, double *integer)

Example

C

// C code to illustrate
// the use of modf function
#include <math.h>
#include <stdio.h>

int main()
{
    double x, fractpart, intpart;

    x = 8.123456;
    fractpart = modf(x, &intpart);

    printf("Integral part = %lf\n", intpart);
    printf("Fraction Part = %lf \n", fractpart);

    return (0);
}

Output

Integral part = 8.000000
Fraction Part = 0.123456 

10. double exp(double x)

The C library function double exp(double x) returns the value of e raised to the x_th power.

Syntax

double exp(double x);

Example

C

// C code to illustrate
// the use of exp function
#include <math.h>
#include <stdio.h>

int main()
{
    double x = 0;

    printf("The exponential value of %lf is %lf\n", x,
           exp(x));
    printf("The exponential value of %lf is %lf\n", x + 1,
           exp(x + 1));
    printf("The exponential value of %lf is %lf\n", x + 2,
           exp(x + 2));

    return (0);
}

Output

The exponential value of 0.000000 is 1.000000
The exponential value of 1.000000 is 2.718282
The exponential value of 2.000000 is 7.389056

11. double cos(double x)

The C library function double cos(double x) returns the cosine of a radian angle x. 

Syntax

double cos(double x);

The same syntax can be used for other trigonometric functions like sin, tan, etc. 

Example

C

// C code to illustrate
// the use of cos function
#include <math.h>
#include <stdio.h>

#define PI 3.14159265

int main()
{
    double x, ret, val;

    x = 60.0;
    val = PI / 180.0;
    ret = cos(x * val);
    printf("The cosine of %lf is %lf degrees\n", x, ret);

    x = 90.0;
    val = PI / 180.0;
    ret = cos(x * val);
    printf("The cosine of %lf is %lf degrees\n", x, ret);

    return (0);
}

Output

The cosine of 60.000000 is 0.500000 degrees
The cosine of 90.000000 is 0.000000 degrees

12. double acos(double x)

The C library function double acos(double x) returns the arc cosine of x in radians.

Syntax

double acos(double x);

The same syntax can be used for other arc trigonometric functions like asin, atan etc.

Example

C

// C code to illustrate
// the use of acos function
#include <math.h>
#include <stdio.h>

#define PI 3.14159265

int main()
{
    double x, ret, val;

    x = 0.9;
    val = 180.0 / PI;

    ret = acos(x) * val;
    printf("The arc cosine of %lf is %lf degrees", x, ret);

    return (0);
}

Output

The arc cosine of 0.900000 is 25.841933 degrees

13. double tanh(double x)

The C library function double tanh(double x) returns the hyperbolic tangent of x.

Syntax

double tanh(double x);

The same syntax can be used for other hyperbolic trigonometric functions like sinh, cosh etc.

Example

C

// C code to illustrate
// the use of tanh function
#include <math.h>
#include <stdio.h>

int main()
{
    double x, ret;
    x = 0.5;

    ret = tanh(x);
    printf("The hyperbolic tangent of %lf is %lf degrees",
           x, ret);

    return (0);
}

Output

The hyperbolic tangent of 0.500000 is 0.462117 degrees

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