module Math

Module Math provides methods for basic trigonometric, logarithmic, and transcendental functions, and for extracting roots.

You can write its constants and method calls thus:

Math::PI      # => 3.141592653589793
Math::E       # => 2.718281828459045
Math.sin(0.0) # => 0.0
Math.cos(0.0) # => 1.0

If you include module Math, you can write simpler forms:

include Math
PI       # => 3.141592653589793
E        # => 2.718281828459045
sin(0.0) # => 0.0
cos(0.0) # => 1.0

For simplicity, the examples here assume:

include Math
INFINITY = Float::INFINITY

The domains and ranges for the methods are denoted by open or closed intervals, using, respectively, parentheses or square brackets:

Many values returned by Math methods are numerical approximations. This is because many such values are, in mathematics, of infinite precision, while in numerical computation the precision is finite.

Thus, in mathematics, cos(π/2) is exactly zero, but in our computation cos(PI/2) is a number very close to zero:

cos(PI/2) # => 6.123031769111886e-17

For very large and very small returned values, we have added formatted numbers for clarity:

tan(PI/2)  # => 1.633123935319537e+16   # 16331239353195370.0
tan(PI)    # => -1.2246467991473532e-16 # -0.0000000000000001

See class Float for the constants that affect Ruby’s floating-point arithmetic.

What’s Here ↑

Trigonometric Functions ↑

Inverse Trigonometric Functions ↑

Hyperbolic Trigonometric Functions ↑

Inverse Hyperbolic Trigonometric Functions ↑

Exponentiation and Logarithmic Functions ↑

Fraction and Exponent Functions ↑

Root Functions ↑

Error Functions ↑

Gamma Functions ↑

Hypotenuse Function ↑

Constants

E

Definition of the mathematical constant E for Euler’s number (e) as a Float number.

PI

Definition of the mathematical constant PI as a Float number.

Public Class Methods

acos(x) → float

Returns the arc cosine of x.

  • Domain: [-1, 1].

  • Range: [0, PI].

Examples:

acos(-1.0) # => 3.141592653589793  # PI
acos(0.0)  # => 1.5707963267948966 # PI/2
acos(1.0)  # => 0.0

static VALUE
math_acos(VALUE unused_obj, VALUE x)
{
    math_arc(x, acos)
}
acosh(x) → float

Returns the inverse hyperbolic cosine of x.

  • Domain: [1, INFINITY].

  • Range: [0, INFINITY].

Examples:

acosh(1.0)      # => 0.0
acosh(INFINITY) # => Infinity

static VALUE
math_acosh(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_min(d, 1.0, "acosh");
    return DBL2NUM(acosh(d));
}
asin(x) → float

Returns the arc sine of x.

  • Domain: [-1, -1].

  • Range: [-PI/2, PI/2].

Examples:

asin(-1.0) # => -1.5707963267948966 # -PI/2
asin(0.0)  # => 0.0
asin(1.0)  # => 1.5707963267948966  # PI/2

static VALUE
math_asin(VALUE unused_obj, VALUE x)
{
    math_arc(x, asin)
}
asinh(x) → float

Returns the inverse hyperbolic sine of x.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-INFINITY, INFINITY].

Examples:

asinh(-INFINITY) # => -Infinity
asinh(0.0)       # => 0.0
asinh(INFINITY)  # => Infinity

static VALUE
math_asinh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(asinh(Get_Double(x)));
}
atan(x) → Float

Returns the arc tangent of x.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-PI/2, PI/2] .

Examples:

atan(-INFINITY) # => -1.5707963267948966 # -PI2
atan(-PI)       # => -1.2626272556789115
atan(-PI/2)     # => -1.0038848218538872
atan(0.0)       # => 0.0
atan(PI/2)      # => 1.0038848218538872
atan(PI)        # => 1.2626272556789115
atan(INFINITY)  # => 1.5707963267948966  # PI/2

static VALUE
math_atan(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(atan(Get_Double(x)));
}
atan2(y, x) → float

Returns the arc tangent of y and x in radians.

  • Domain of y: [-INFINITY, INFINITY].

  • Domain of x: [-INFINITY, INFINITY].

  • Range: [-PI, PI].

Examples:

atan2(-1.0, -1.0) # => -2.356194490192345  # -3*PI/4
atan2(-1.0, 0.0)  # => -1.5707963267948966 # -PI/2
atan2(-1.0, 1.0)  # => -0.7853981633974483 # -PI/4
atan2(0.0, -1.0)  # => 3.141592653589793   # PI

static VALUE
math_atan2(VALUE unused_obj, VALUE y, VALUE x)
{
    double dx, dy;
    dx = Get_Double(x);
    dy = Get_Double(y);
    if (dx == 0.0 && dy == 0.0) {
        if (!signbit(dx))
            return DBL2NUM(dy);
        if (!signbit(dy))
            return DBL2NUM(M_PI);
        return DBL2NUM(-M_PI);
    }
#ifndef ATAN2_INF_C99
    if (isinf(dx) && isinf(dy)) {
        /* optimization for FLONUM */
        if (dx < 0.0) {
            const double dz = (3.0 * M_PI / 4.0);
            return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
        }
        else {
            const double dz = (M_PI / 4.0);
            return (dy < 0.0) ? DBL2NUM(-dz) : DBL2NUM(dz);
        }
    }
#endif
    return DBL2NUM(atan2(dy, dx));
}
atanh(x) → float

Returns the inverse hyperbolic tangent of x.

  • Domain: [-1, 1].

  • Range: [-INFINITY, INFINITY].

Examples:

atanh(-1.0) # => -Infinity
atanh(0.0)  # => 0.0
atanh(1.0)  # => Infinity

static VALUE
math_atanh(VALUE unused_obj, VALUE x)
{
    double d;

    d = Get_Double(x);
    domain_check_range(d, -1.0, +1.0, "atanh");
    /* check for pole error */
    if (d == -1.0) return DBL2NUM(-HUGE_VAL);
    if (d == +1.0) return DBL2NUM(+HUGE_VAL);
    return DBL2NUM(atanh(d));
}
cbrt(x) → float

Returns the cube root of x.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-INFINITY, INFINITY].

Examples:

cbrt(-INFINITY) # => -Infinity
cbrt(-27.0)     # => -3.0
cbrt(-8.0)      # => -2.0
cbrt(-2.0)      # => -1.2599210498948732
cbrt(1.0)       # => 1.0
cbrt(0.0)       # => 0.0
cbrt(1.0)       # => 1.0
cbrt(2.0)       # => 1.2599210498948732
cbrt(8.0)       # => 2.0
cbrt(27.0)      # => 3.0
cbrt(INFINITY)  # => Infinity

static VALUE
math_cbrt(VALUE unused_obj, VALUE x)
{
    double f = Get_Double(x);
    double r = cbrt(f);
#if defined __GLIBC__
    if (isfinite(r) && !(f == 0.0 && r == 0.0)) {
        r = (2.0 * r + (f / r / r)) / 3.0;
    }
#endif
    return DBL2NUM(r);
}
cos(x) → float

Returns the cosine of x in radians.

  • Domain: (-INFINITY, INFINITY).

  • Range: [-1.0, 1.0].

Examples:

cos(-PI)   # => -1.0
cos(-PI/2) # => 6.123031769111886e-17 # 0.0000000000000001
cos(0.0)   # => 1.0
cos(PI/2)  # => 6.123031769111886e-17 # 0.0000000000000001
cos(PI)    # => -1.0

static VALUE
math_cos(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(cos(Get_Double(x)));
}
cosh(x) → float

Returns the hyperbolic cosine of x in radians.

  • Domain: [-INFINITY, INFINITY].

  • Range: [1, INFINITY].

Examples:

cosh(-INFINITY) # => Infinity
cosh(0.0)       # => 1.0
cosh(INFINITY)  # => Infinity

static VALUE
math_cosh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(cosh(Get_Double(x)));
}
erf(x) → float

Returns the value of the Gauss error function for x.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-1, 1].

Examples:

erf(-INFINITY) # => -1.0
erf(0.0)       # => 0.0
erf(INFINITY)  # => 1.0

Related: Math.erfc.

static VALUE
math_erf(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(erf(Get_Double(x)));
}
erfc(x) → Float

Returns the value of the complementary error function for x.

  • Domain: [-INFINITY, INFINITY].

  • Range: [0, 2].

Examples:

erfc(-INFINITY) # => 2.0
erfc(0.0)       # => 1.0
erfc(INFINITY)  # => 0.0

Related: Math.erf.

static VALUE
math_erfc(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(erfc(Get_Double(x)));
}
exp(x) → float

Returns e raised to the x power.

  • Domain: [-INFINITY, INFINITY].

  • Range: [0, INFINITY].

Examples:

exp(-INFINITY) # => 0.0
exp(-1.0)      # => 0.36787944117144233 # 1.0/E
exp(0.0)       # => 1.0
exp(0.5)       # => 1.6487212707001282  # sqrt(E)
exp(1.0)       # => 2.718281828459045   # E
exp(2.0)       # => 7.38905609893065    # E**2
exp(INFINITY)  # => Infinity

static VALUE
math_exp(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(exp(Get_Double(x)));
}
frexp(x) → [fraction, exponent]

Returns a 2-element array containing the normalized signed float fraction and integer exponent of x such that:

x = fraction * 2**exponent

See IEEE 754 double-precision binary floating-point format: binary64.

  • Domain: [-INFINITY, INFINITY].

  • Range [-INFINITY, INFINITY].

Examples:

frexp(-INFINITY) # => [-Infinity, -1]
frexp(-2.0)      # => [-0.5, 2]
frexp(-1.0)      # => [-0.5, 1]
frexp(0.0)       # => [0.0, 0]
frexp(1.0)       # => [0.5, 1]
frexp(2.0)       # => [0.5, 2]
frexp(INFINITY)  # => [Infinity, -1]

Related: Math.ldexp (inverse of Math.frexp).

static VALUE
math_frexp(VALUE unused_obj, VALUE x)
{
    double d;
    int exp;

    d = frexp(Get_Double(x), &exp);
    return rb_assoc_new(DBL2NUM(d), INT2NUM(exp));
}
gamma(x) → float

Returns the value of the gamma function for x.

  • Domain: (-INFINITY, INFINITY] excluding negative integers.

  • Range: [-INFINITY, INFINITY].

Examples:

gamma(-2.5)      # => -0.9453087204829431
gamma(-1.5)      # => 2.3632718012073513
gamma(-0.5)      # => -3.5449077018110375
gamma(0.0)      # => Infinity
gamma(1.0)      # => 1.0
gamma(2.0)      # => 1.0
gamma(3.0)      # => 2.0
gamma(4.0)      # => 6.0
gamma(5.0)      # => 24.0

Related: Math.lgamma.

static VALUE
math_gamma(VALUE unused_obj, VALUE x)
{
    static const double fact_table[] = {
        /* fact(0) */ 1.0,
        /* fact(1) */ 1.0,
        /* fact(2) */ 2.0,
        /* fact(3) */ 6.0,
        /* fact(4) */ 24.0,
        /* fact(5) */ 120.0,
        /* fact(6) */ 720.0,
        /* fact(7) */ 5040.0,
        /* fact(8) */ 40320.0,
        /* fact(9) */ 362880.0,
        /* fact(10) */ 3628800.0,
        /* fact(11) */ 39916800.0,
        /* fact(12) */ 479001600.0,
        /* fact(13) */ 6227020800.0,
        /* fact(14) */ 87178291200.0,
        /* fact(15) */ 1307674368000.0,
        /* fact(16) */ 20922789888000.0,
        /* fact(17) */ 355687428096000.0,
        /* fact(18) */ 6402373705728000.0,
        /* fact(19) */ 121645100408832000.0,
        /* fact(20) */ 2432902008176640000.0,
        /* fact(21) */ 51090942171709440000.0,
        /* fact(22) */ 1124000727777607680000.0,
        /* fact(23)=25852016738884976640000 needs 56bit mantissa which is
         * impossible to represent exactly in IEEE 754 double which have
         * 53bit mantissa. */
    };
    enum {NFACT_TABLE = numberof(fact_table)};
    double d;
    d = Get_Double(x);
    /* check for domain error */
    if (isinf(d)) {
        if (signbit(d)) domain_error("gamma");
        return DBL2NUM(HUGE_VAL);
    }
    if (d == 0.0) {
        return signbit(d) ? DBL2NUM(-HUGE_VAL) : DBL2NUM(HUGE_VAL);
    }
    if (d == floor(d)) {
        domain_check_min(d, 0.0, "gamma");
        if (1.0 <= d && d <= (double)NFACT_TABLE) {
            return DBL2NUM(fact_table[(int)d - 1]);
        }
    }
    return DBL2NUM(tgamma(d));
}
hypot(a, b) → float

Returns sqrt(a**2 + b**2), which is the length of the longest side c (the hypotenuse) of the right triangle whose other sides have lengths a and b.

  • Domain of a: [-INFINITY, INFINITY].

  • Domain of +ab: [-INFINITY, INFINITY].

  • Range: [0, INFINITY].

Examples:

hypot(0.0, 1.0)       # => 1.0
hypot(1.0, 1.0)       # => 1.4142135623730951 # sqrt(2.0)
hypot(3.0, 4.0)       # => 5.0
hypot(5.0, 12.0)      # => 13.0
hypot(1.0, sqrt(3.0)) # => 1.9999999999999998 # Near 2.0

Note that if either argument is INFINITY or -INFINITY, the result is Infinity.

static VALUE
math_hypot(VALUE unused_obj, VALUE x, VALUE y)
{
    return DBL2NUM(hypot(Get_Double(x), Get_Double(y)));
}
ldexp(fraction, exponent) → float

Returns the value of fraction * 2**exponent.

  • Domain of fraction: [0.0, 1.0).

  • Domain of exponent: [0, 1024] (larger values are equivalent to 1024).

See IEEE 754 double-precision binary floating-point format: binary64.

Examples:

ldexp(-INFINITY, -1) # => -Infinity
ldexp(-0.5, 2)       # => -2.0
ldexp(-0.5, 1)       # => -1.0
ldexp(0.0, 0)        # => 0.0
ldexp(-0.5, 1)       # => 1.0
ldexp(-0.5, 2)       # => 2.0
ldexp(INFINITY, -1)  # => Infinity

Related: Math.frexp (inverse of Math.ldexp).

static VALUE
math_ldexp(VALUE unused_obj, VALUE x, VALUE n)
{
    return DBL2NUM(ldexp(Get_Double(x), NUM2INT(n)));
}
lgamma(x) → [float, -1 or 1]

Returns a 2-element array equivalent to:

[Math.log(Math.gamma(x).abs), Math.gamma(x) < 0 ? -1 : 1]

See logarithmic gamma function.

  • Domain: (-INFINITY, INFINITY].

  • Range of first element: (-INFINITY, INFINITY].

  • Second element is -1 or 1.

Examples:

lgamma(-4.0) # => [Infinity, -1]
lgamma(-3.0) # => [Infinity, -1]
lgamma(-2.0) # => [Infinity, -1]
lgamma(-1.0) # => [Infinity, -1]
lgamma(0.0)  # => [Infinity, 1]

lgamma(1.0)  # => [0.0, 1]
lgamma(2.0)  # => [0.0, 1]
lgamma(3.0)  # => [0.6931471805599436, 1]
lgamma(4.0)  # => [1.7917594692280545, 1]

lgamma(-2.5) # => [-0.05624371649767279, -1]
lgamma(-1.5) # => [0.8600470153764797, 1]
lgamma(-0.5) # => [1.265512123484647, -1]
lgamma(0.5)  # => [0.5723649429247004, 1]
lgamma(1.5)  # => [-0.12078223763524676, 1]
lgamma(2.5)      # => [0.2846828704729205, 1]

Related: Math.gamma.

static VALUE
math_lgamma(VALUE unused_obj, VALUE x)
{
    double d;
    int sign=1;
    VALUE v;
    d = Get_Double(x);
    /* check for domain error */
    if (isinf(d)) {
        if (signbit(d)) domain_error("lgamma");
        return rb_assoc_new(DBL2NUM(HUGE_VAL), INT2FIX(1));
    }
    if (d == 0.0) {
        VALUE vsign = signbit(d) ? INT2FIX(-1) : INT2FIX(+1);
        return rb_assoc_new(DBL2NUM(HUGE_VAL), vsign);
    }
    v = DBL2NUM(lgamma_r(d, &sign));
    return rb_assoc_new(v, INT2FIX(sign));
}
log(x, base = Math::E) → Float

Returns the base base logarithm of x.

  • Domain: [0, INFINITY].

  • Range: [-INFINITY, INFINITY)].

Examples:

log(0.0)        # => -Infinity
log(1.0)        # => 0.0
log(E)          # => 1.0
log(INFINITY)   # => Infinity

log(0.0, 2.0)   # => -Infinity
log(1.0, 2.0)   # => 0.0
log(2.0, 2.0)   # => 1.0

log(0.0, 10.0)  # => -Infinity
log(1.0, 10.0)  # => 0.0
log(10.0, 10.0) # => 1.0

static VALUE
math_log(int argc, const VALUE *argv, VALUE unused_obj)
{
    return rb_math_log(argc, argv);
}
log10(x) → float

Returns the base 10 logarithm of x.

  • Domain: [0, INFINITY].

  • Range: [-INFINITY, INFINITY].

Examples:

log10(0.0)      # => -Infinity
log10(1.0)      # => 0.0
log10(10.0)     # => 1.0
log10(INFINITY) # => Infinity

static VALUE
math_log10(VALUE unused_obj, VALUE x)
{
    size_t numbits;
    double d = get_double_rshift(x, &numbits);

    domain_check_min(d, 0.0, "log10");
    /* check for pole error */
    if (d == 0.0) return DBL2NUM(-HUGE_VAL);

    return DBL2NUM(log10(d) + numbits * log10(2)); /* log10(d * 2 ** numbits) */
}
log2(x) → float

Returns the base 2 logarithm of x.

  • Domain: [0, INFINITY].

  • Range: [-INFINITY, INFINITY].

Examples:

log2(0.0)      # => -Infinity
log2(1.0)      # => 0.0
log2(2.0)      # => 1.0
log2(INFINITY) # => Infinity

static VALUE
math_log2(VALUE unused_obj, VALUE x)
{
    size_t numbits;
    double d = get_double_rshift(x, &numbits);

    domain_check_min(d, 0.0, "log2");
    /* check for pole error */
    if (d == 0.0) return DBL2NUM(-HUGE_VAL);

    return DBL2NUM(log2(d) + numbits); /* log2(d * 2 ** numbits) */
}
sin(x) → float

Returns the sine of x in radians.

  • Domain: (-INFINITY, INFINITY).

  • Range: [-1.0, 1.0].

Examples:

sin(-PI)   # => -1.2246063538223773e-16 # -0.0000000000000001
sin(-PI/2) # => -1.0
sin(0.0)   # => 0.0
sin(PI/2)  # => 1.0
sin(PI)    # => 1.2246063538223773e-16  # 0.0000000000000001

static VALUE
math_sin(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(sin(Get_Double(x)));
}
sinh(x) → float

Returns the hyperbolic sine of x in radians.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-INFINITY, INFINITY].

Examples:

sinh(-INFINITY) # => -Infinity
sinh(0.0)       # => 0.0
sinh(INFINITY)  # => Infinity

static VALUE
math_sinh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(sinh(Get_Double(x)));
}
sqrt(x) → float

Returns the principal (non-negative) square root of x.

  • Domain: [0, INFINITY].

  • Range: [0, INFINITY].

Examples:

sqrt(0.0)      # => 0.0
sqrt(0.5)      # => 0.7071067811865476
sqrt(1.0)      # => 1.0
sqrt(2.0)      # => 1.4142135623730951
sqrt(4.0)      # => 2.0
sqrt(9.0)      # => 3.0
sqrt(INFINITY) # => Infinity

static VALUE
math_sqrt(VALUE unused_obj, VALUE x)
{
    return rb_math_sqrt(x);
}
tan(x) → float

Returns the tangent of x in radians.

  • Domain: (-INFINITY, INFINITY).

  • Range: (-INFINITY, INFINITY).

Examples:

tan(-PI)   # => 1.2246467991473532e-16  # -0.0000000000000001
tan(-PI/2) # => -1.633123935319537e+16  # -16331239353195370.0
tan(0.0)   # => 0.0
tan(PI/2)  # => 1.633123935319537e+16   # 16331239353195370.0
tan(PI)    # => -1.2246467991473532e-16 # -0.0000000000000001

static VALUE
math_tan(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(tan(Get_Double(x)));
}
tanh(x) → float

Returns the hyperbolic tangent of x in radians.

  • Domain: [-INFINITY, INFINITY].

  • Range: [-1, 1].

Examples:

tanh(-INFINITY) # => -1.0
tanh(0.0)       # => 0.0
tanh(INFINITY)  # => 1.0

static VALUE
math_tanh(VALUE unused_obj, VALUE x)
{
    return DBL2NUM(tanh(Get_Double(x)));
}