# <!-- rdoc-file=math.c -->
# 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:
#
# *   An open interval does not include the endpoints:
#
#         (-INFINITY, INFINITY)
#
# *   A closed interval includes the endpoints:
#
#         [-1.0, 1.0]
#
# *   A half-open interval includes one endpoint, but not the other:
#
#         [1.0, INFINITY)
#
#
# 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
#
# *   ::cos: Returns the cosine of the given argument.
# *   ::sin: Returns the sine of the given argument.
# *   ::tan: Returns the tangent of the given argument.
#
#
# #### Inverse Trigonometric Functions
#
# *   ::acos: Returns the arc cosine of the given argument.
# *   ::asin: Returns the arc sine of the given argument.
# *   ::atan: Returns the arc tangent of the given argument.
# *   ::atan2: Returns the arg tangent of two given arguments.
#
#
# #### Hyperbolic Trigonometric Functions
#
# *   ::cosh: Returns the hyperbolic cosine of the given argument.
# *   ::sinh: Returns the hyperbolic sine of the given argument.
# *   ::tanh: Returns the hyperbolic tangent of the given argument.
#
#
# #### Inverse Hyperbolic Trigonometric Functions
#
# *   ::acosh: Returns the inverse hyperbolic cosine of the given argument.
# *   ::asinh: Returns the inverse hyperbolic sine of the given argument.
# *   ::atanh: Returns the inverse hyperbolic tangent of the given argument.
#
#
# #### Exponentiation and Logarithmic Functions
#
# *   ::exp: Returns the value of a given value raised to a given power.
# *   ::log: Returns the logarithm of a given value in a given base.
# *   ::log10: Returns the base 10 logarithm of the given argument.
# *   ::log2: Returns the base 2 logarithm of the given argument.
#
#
# #### Fraction and Exponent Functions
#
# *   ::frexp: Returns the fraction and exponent of the given argument.
# *   ::ldexp: Returns the value for a given fraction and exponent.
#
#
# #### Root Functions
#
# *   ::cbrt: Returns the cube root of the given argument.
# *   ::sqrt: Returns the square root of the given argument.
#
#
# #### Error Functions
#
# *   ::erf: Returns the value of the Gauss error function for the given
#     argument.
# *   ::erfc: Returns the value of the complementary error function for the
#     given argument.
#
#
# #### Gamma Functions
#
# *   ::gamma: Returns the value of the gamma function for the given argument.
# *   ::lgamma: Returns the value of the logarithmic gamma function for the
#     given argument.
#
#
# #### Hypotenuse Function
#
# *   ::hypot: Returns `sqrt(a**2 + b**2)` for the given `a` and `b`.
#
module Math
  # <!-- rdoc-file=math.c -->
  # Definition of the mathematical constant E for Euler's number (e) as a Float
  # number.
  #
  E: Float

  # <!-- rdoc-file=math.c -->
  # Definition of the mathematical constant PI as a Float number.
  #
  PI: Float

  # <!-- rdoc-file=math.c -->
  # Raised when a mathematical function is evaluated outside of its domain of
  # definition.
  #
  # For example, since `cos` returns values in the range -1..1, its inverse
  # function `acos` is only defined on that interval:
  #
  #     Math.acos(42)
  #
  # *produces:*
  #
  #     Math::DomainError: Numerical argument is out of domain - "acos"
  #
  class DomainError < StandardError
  end

  # A type that's passable to `Math` functions: A `Numeric` type that defines `.to_f`.
  #
  type double = Numeric & _ToF

  # <!--
  #   rdoc-file=math.c
  #   - Math.acos(x) -> float
  # -->
  # Returns the [arc
  # cosine](https://en.wikipedia.org/wiki/Inverse_trigonometric_functions) 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
  #
  def self.acos: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.acosh(x) -> float
  # -->
  # Returns the [inverse hyperbolic
  # cosine](https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions) of `x`.
  #
  # *   Domain: `[1, INFINITY]`.
  # *   Range: `[0, INFINITY]`.
  #
  #
  # Examples:
  #
  #     acosh(1.0)      # => 0.0
  #     acosh(INFINITY) # => Infinity
  #
  def self.acosh: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.asin(x) -> float
  # -->
  # Returns the [arc
  # sine](https://en.wikipedia.org/wiki/Inverse_trigonometric_functions) 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
  #
  def self.asin: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.asinh(x) -> float
  # -->
  # Returns the [inverse hyperbolic
  # sine](https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions) of `x`.
  #
  # *   Domain: `[-INFINITY, INFINITY]`.
  # *   Range: `[-INFINITY, INFINITY]`.
  #
  #
  # Examples:
  #
  #     asinh(-INFINITY) # => -Infinity
  #     asinh(0.0)       # => 0.0
  #     asinh(INFINITY)  # => Infinity
  #
  def self.asinh: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.atan(x)    -> Float
  # -->
  # Returns the [arc
  # tangent](https://en.wikipedia.org/wiki/Inverse_trigonometric_functions) 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
  #
  def self.atan: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.atan2(y, x) -> float
  # -->
  # Returns the [arc tangent](https://en.wikipedia.org/wiki/Atan2) of `y` and `x`
  # in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   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
  #
  def self.atan2: (double y, double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.atanh(x) -> float
  # -->
  # Returns the [inverse hyperbolic
  # tangent](https://en.wikipedia.org/wiki/Inverse_hyperbolic_functions) of `x`.
  #
  # *   Domain: `[-1, 1]`.
  # *   Range: `[-INFINITY, INFINITY]`.
  #
  #
  # Examples:
  #
  #     atanh(-1.0) # => -Infinity
  #     atanh(0.0)  # => 0.0
  #     atanh(1.0)  # => Infinity
  #
  def self.atanh: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.cbrt(x) -> float
  # -->
  # Returns the [cube root](https://en.wikipedia.org/wiki/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
  #
  def self.cbrt: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.cos(x) -> float
  # -->
  # Returns the [cosine](https://en.wikipedia.org/wiki/Sine_and_cosine) of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   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
  #
  def self.cos: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.cosh(x) -> float
  # -->
  # Returns the [hyperbolic
  # cosine](https://en.wikipedia.org/wiki/Hyperbolic_functions) of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   Domain: `[-INFINITY, INFINITY]`.
  # *   Range: `[1, INFINITY]`.
  #
  #
  # Examples:
  #
  #     cosh(-INFINITY) # => Infinity
  #     cosh(0.0)       # => 1.0
  #     cosh(INFINITY)  # => Infinity
  #
  def self.cosh: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.erf(x) -> float
  # -->
  # Returns the value of the [Gauss error
  # function](https://en.wikipedia.org/wiki/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.
  #
  def self.erf: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.erfc(x)  -> Float
  # -->
  # Returns the value of the [complementary error
  # function](https://en.wikipedia.org/wiki/Error_function#Complementary_error_fun
  # ction) 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.
  #
  def self.erfc: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.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
  #
  def self.exp: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.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](https://en.wikipedia.org/wiki/Double-precision_floating-point_format
  # #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).
  #
  def self.frexp: (double x) -> [Float, Integer]

  # <!--
  #   rdoc-file=math.c
  #   - Math.gamma(x) -> float
  # -->
  # Returns the value of the [gamma
  # function](https://en.wikipedia.org/wiki/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.
  #
  def self.gamma: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.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`.
  #
  def self.hypot: (double x, double y) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.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](https://en.wikipedia.org/wiki/Double-precision_floating-point_format
  # #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).
  #
  def self.ldexp: (double fraction, int exponent) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.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](https://en.wikipedia.org/wiki/Gamma_function#The_log-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.
  #
  def self.lgamma: (double x) -> [Float, -1 | 1]

  # <!--
  #   rdoc-file=math.c
  #   - Math.log(x, base = Math::E) -> Float
  # -->
  # Returns the base `base` [logarithm](https://en.wikipedia.org/wiki/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
  #
  def self.log: (double x, ?double base) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.log10(x) -> float
  # -->
  # Returns the base 10 [logarithm](https://en.wikipedia.org/wiki/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
  #
  def self.log10: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.log2(x) -> float
  # -->
  # Returns the base 2 [logarithm](https://en.wikipedia.org/wiki/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
  #
  def self.log2: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.sin(x) -> float
  # -->
  # Returns the [sine](https://en.wikipedia.org/wiki/Sine_and_cosine) of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   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
  #
  def self.sin: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.sinh(x) -> float
  # -->
  # Returns the [hyperbolic
  # sine](https://en.wikipedia.org/wiki/Hyperbolic_functions) of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   Domain: `[-INFINITY, INFINITY]`.
  # *   Range: `[-INFINITY, INFINITY]`.
  #
  #
  # Examples:
  #
  #     sinh(-INFINITY) # => -Infinity
  #     sinh(0.0)       # => 0.0
  #     sinh(INFINITY)  # => Infinity
  #
  def self.sinh: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.sqrt(x) -> float
  # -->
  # Returns the principal (non-negative) [square
  # root](https://en.wikipedia.org/wiki/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
  #
  def self.sqrt: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.tan(x) -> float
  # -->
  # Returns the [tangent](https://en.wikipedia.org/wiki/Trigonometric_functions)
  # of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   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
  #
  def self.tan: (double x) -> Float

  # <!--
  #   rdoc-file=math.c
  #   - Math.tanh(x) -> float
  # -->
  # Returns the [hyperbolic
  # tangent](https://en.wikipedia.org/wiki/Hyperbolic_functions) of `x` in
  # [radians](https://en.wikipedia.org/wiki/Trigonometric_functions#Radians_versus
  # _degrees).
  #
  # *   Domain: `[-INFINITY, INFINITY]`.
  # *   Range: `[-1, 1]`.
  #
  #
  # Examples:
  #
  #     tanh(-INFINITY) # => -1.0
  #     tanh(0.0)       # => 0.0
  #     tanh(INFINITY)  # => 1.0
  #
  def self.tanh: (double x) -> Float
end