C Library - math.h

The <math.h> header file in C provides a collection of standard mathematical functions and predefined constants for performing mathematical operations. These functions generally accept double values as arguments and return double results.

• Supports common operations such as square root, power, logarithmic, and trigonometric calculations.
• Includes predefined mathematical constants and utility functions for accurate computations.

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

int main() {
    double num = 25.0;

    printf("Square Root = %.2f\n", sqrt(num));
    printf("Power = %.2f\n", pow(2, 3));

    return 0;
}

Square Root = 5.00
Power = 8.00

Syntax

#include <math.h>

After including the header file, we can use its services in the program. There are two types of elements in math.h header file:

• Functions
• Macros

math.h Library Functions

These are functions that are defined inside the <math.h> header file that performs a particular mathematical operation when called.

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

int main()
{
    // two variables for test
    double x = 3.3, y = 1.1;

    // ceil and floor demonstration
    printf(
        "Ceil of %.1lf = %.1lf \nFloor of %.1lf = %.1lf\n",
        x, ceil(x), x, floor(x));

    // pow function demonstration
    printf("%.1lf raised to the power %.1lf = %.1lf\n", x,
           y, pow(x, y));
  
    return 0;
}

Ceil of 3.3 = 4.0 
Floor of 3.3 = 3.0
3.3 raised to the power 1.1 = 3.7

Commonly used math.h header file functions

math.h Library Macros

They are the macros defined inside <math.h> header file using #define preprocessor. They can be either constant that is replaced by their value when used or either function-like macros.

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

int main()
{
    // HUGE_VAL macro
    printf("Value Returned by HUGE_VAL = %.1lf\n", HUGE_VAL);

    // isgreater macro demonstration
    printf("Value returned by isgreater = %d", isgreater(12.0, 13.0));
  
    return 0;
}

Value Returned by HUGE_VAL = inf
Value returned by isgreater = 0

double cos(double x)

This function returns the cosine of x, where x is an angle in radians.

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

int main(void)
{
    double x = 1.5;
    double y = 2.0;
    double z;

    z = sin(x);
    printf("sin(%.2lf) = %.2lf\n", x, z);
    // output: sin(1.50) = 0.99

    z = cos(x);
    printf("cos(%.2lf) = %.2lf\n", x, z);
    // output: cos(1.50) = 0.07

    z = tan(x);
    printf("tan(%.2lf) = %lf\n", x, z);
    // output: tan(1.50) = 14.33

    z = asin(x);
    printf("asin(%.2lf) = %lf\n", x, z);
    // output: asin(1.50) = NAN

    z = acos(x);
    printf("acos(%.2lf) = %lf\n", x, z);
    // output: acos(1.50) = NAN

    z = atan(x);
    printf("atan(%.2lf) = %lf\n", x, z);
    // output: atan(1.50) = 0.98

    z = exp(y);
    printf("exp(%.2lf) = %lf\n", y, z);
    // output: exp(2.00) = 7.39

    z = log(y);
    printf("log(%.2lf) = %lf\n", y, z);
    // output: log(2.00) = 0.69

    z = sqrt(y);
    printf("sqrt(%.2lf) = %lf\n", y, z);
    // output: sqrt(2.00) = 1.41

    return 0;
}

Output

sin(1.50) = 0.997495
cos(1.50) = 0.070737
tan(1.50) = 14.101420
asin(1.50) = nan
acos(1.50) = nan
atan(1.50) = 0.982794
exp(2.00) = 7.389056
log(2.00) = 0.693147
sqrt(2.00) = 1.414214

Note: inf is used to represent positive infinity (very large number that cannot be represented using double or float.

Here is a list of some commonly used math.h library macros:

Note: isgreater(x , y) may look like a function but they are defined as macros in the math.h header file and are replaced by their value in preprocessing.