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    Mathematical Functions

    • Introduction
    • Installing/Configuring
    • Predefined Constants
    • Math Functions
      • abs — Absolute value
      • acos — Arc cosine
      • acosh — Inverse hyperbolic cosine
      • asin — Arc sine
      • asinh — Inverse hyperbolic sine
      • atan2 — Arc tangent of two variables
      • atan — Arc tangent
      • atanh — Inverse hyperbolic tangent
      • base_convert — Convert a number between arbitrary bases
      • bindec — Binary to decimal
      • ceil — Round fractions up
      • cos — Cosine
      • cosh — Hyperbolic cosine
      • decbin — Decimal to binary
      • dechex — Decimal to hexadecimal
      • decoct — Decimal to octal
      • deg2rad — Converts the number in degrees to the radian equivalent
      • exp — Calculates the exponent of e
      • expm1 — Returns exp($num) - 1, computed in a way that is accurate even when the value of number is close to zero
      • fdiv — Divides two numbers, according to IEEE 754
      • floor — Round fractions down
      • fmod — Returns the floating point remainder (modulo) of the division of the arguments
      • hexdec — Hexadecimal to decimal
      • hypot — Calculate the length of the hypotenuse of a right-angle triangle
      • intdiv — Integer division
      • is_finite — Checks whether a float is finite
      • is_infinite — Checks whether a float is infinite
      • is_nan — Checks whether a float is NAN
      • log10 — Base-10 logarithm
      • log1p — Returns log(1 + number), computed in a way that is accurate even when the value of number is close to zero
      • log — Natural logarithm
      • max — Find highest value
      • min — Find lowest value
      • octdec — Octal to decimal
      • pi — Get value of pi
      • pow — Exponential expression
      • rad2deg — Converts the radian number to the equivalent number in degrees
      • round — Rounds a float
      • sin — Sine
      • sinh — Hyperbolic sine
      • sqrt — Square root
      • tan — Tangent
      • tanh — Hyperbolic tangent
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    User Contributed Notes 1 note

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    -130
    Hayley Watson
    11 years ago
    Provides a function to rescale numbers so that the range [a,b] fits into the range [c,d].

    <?php
    function rescale($ab, $cd)
    {
        list(    $a, $b) = $ab;
        list(    $c, $d) = $cd;
        if(    $a == $b)
        {
                trigger_error("Invalid scale", E_USER_WARNING);
            return     false;
        }
            $o = ($b * $c - $a * $d) / ($b - $a);
            $s = ($d - $c) / ($b - $a);
        return function(    $x)use($o, $s)
        {
            return     $s * $x + $o;
        };
    }

    $fahr2celsius = rescale([32, 212], [0, 100]);
    echo      $fahr2celsius(98.6); // 37°C

    ?>
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