<math.h>

<math.h> provides standard math functions: trigonometric, exponential, logarithmic, rounding, and IEEE 754 utilities (isnan, isinf). Append f for float or l for long double versions.

Compile with -lm to link the math library.

This example demonstrates basic math functions and special-value checking.

// compile: gcc -o mathexample mathexample.c -lm
// run: ./mathexample
// description: math functions and special value detection
 
#include <math.h>
#include <stdio.h>
 
int main() {
    printf("sqrt(2) = %.6f\n", sqrt(2.0));
    printf("sin(pi/4) = %.6f\n", sin(M_PI / 4));
    printf("exp(1) = %.6f\n", exp(1.0));
    printf("log(10) = %.6f\n", log(10.0));
 
    double nan_val = 0.0 / 0.0;
    double inf_val = 1.0 / 0.0;
    printf("isnan(nan): %d, isinf(inf): %d\n", isnan(nan_val), isinf(inf_val));
 
    return 0;
}

Root and power:

• sqrt(x): square root
• cbrt(x): cube root
• pow(x, y): x to power y
• hypot(x, y): sqrt(x² + y²) without overflow

Exponential and logarithm:

• exp(x), exp2(x), exp10(x): e^x, 2^x, 10^x
• expm1(x): e^x - 1 (accurate for small x)
• log(x), log2(x), log10(x): natural, base-2, base-10 logarithm
• log1p(x): log(1 + x) (accurate for small x)

Trigonometric (argument in radians):

• sin(x), cos(x), tan(x)
• asin(x), acos(x), atan(x): inverse (range: -π/2 to π/2)
• atan2(y, x): inverse with quadrant correction

Hyperbolic:

• sinh(x), cosh(x), tanh(x)
• asinh(x), acosh(x), atanh(x): inverse

Rounding:

• ceil(x): round up (smallest integer ≥ x)
• floor(x): round down (largest integer ≤ x)
• round(x): round to nearest integer (0.5 rounds away from zero)
• trunc(x): truncate toward zero
• nearbyint(x): round to nearest using current rounding mode
• rint(x): similar to nearbyint but may raise exception

Absolute value and remainder:

• fabs(x): absolute value (floating-point)
• fmod(x, y): floating-point remainder (sign of x)
• remainder(x, y): IEEE remainder (nearest multiple of y)
• drem(x, y): alias for remainder

Minimum and maximum:

• fmin(x, y): minimum (NaN-safe: returns non-NaN if possible)
• fmax(x, y): maximum

Special value checks:

• isnan(x): check if NaN
• isinf(x): check if infinite
• isfinite(x): check if finite (not NaN or inf)
• isnormal(x): check if normal (not zero, subnormal, inf, or NaN)
• signbit(x): check sign bit

Constants (non-standard; require -D_USE_MATH_DEFINES or -D_GNU_SOURCE):

• M_PI: π
• M_E: e
• M_LN2, M_LN10: ln(2), ln(10)
• M_LOG2E, M_LOG10E: log₂(e), log₁₀(e)
• M_SQRT2, M_SQRT1_2: √2, 1/√2