Math 函数

abs — 绝对值
acos — 反余弦
acosh — 反双曲余弦
asin — 反正弦
asinh — 反双曲正弦
atan — 反正切
atan2 — 两个参数的反正切
atanh — 反双曲正切
base_convert — 在任意进制之间转换数字
bindec — 二进制转换为十进制
ceil — 进一法取整
cos — 余弦
cosh — 双曲余弦
decbin — 十进制转换为二进制
dechex — 十进制转换为十六进制
decoct — 十进制转换为八进制
deg2rad — 将角度转换为弧度
exp — 计算 e 的指数
expm1 — 返回 exp($num) - 1，甚至当 number 的值接近零也能计算出准确结果
fdiv — Divides two numbers, according to IEEE 754
floor — 舍去法取整
fmod — 返回除法的浮点数余数
fpow — Raise one number to the power of another, according to IEEE 754
hexdec — 十六进制转换为十进制
hypot — 计算直角三角形的斜边长度
intdiv — 对除法结果取整
is_finite — 判断浮点数是否是有效的有限值
is_infinite — 判断浮点数是否为无限值
is_nan — 判断浮点数是否是否为 NAN
log — 自然对数
log10 — 以 10 为底的对数
log1p — 返回 log(1 + number)，甚至当 number 的值接近零也能计算出准确结果
max — 找出最大值
min — 找出最小值
octdec — 八进制转换为十进制
pi — 得到圆周率值
pow — 指数表达式
rad2deg — 将弧度数转换为相应的角度数
round — 对浮点数进行四舍五入
sin — 正弦
sinh — 双曲正弦
sqrt — 平方根
tan — 正切
tanh — 双曲正切

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20 years ago

For people interest in Differential Equations, I've done a function that receive a string like: x^2+x^3 and put it in
2x+3x^2 witch is the differantial of the previous equation.

In the code there is one thing missing: the $string{$i} is often going outOfBound (Uninitialized string offset: 6 in...)
if your error setting is set a little too high... I just dont know how to fix this.

So there is the code for differential equation with (+ and -) only:

<?
function differentiel($equa)
{
    $equa = strtolower($equa);
    echo "Equation de depart: ".$equa."<br>";
    $final = ""; 
    
    for($i = 0; $i < strlen($equa); $i++)
    {
        //Make a new string from the receive $equa
        if($equa{$i} == "x" && $equa{$i+1} == "^")
        {
            $final .= $equa{$i+2};
            $final .= "x^";
            $final .= $equa{$i+2}-1;
        }
        elseif($equa{$i} == "+" || $equa{$i} == "-")
        {
            $final .= $equa{$i};
        }
        elseif(is_numeric($equa{$i}) && $i == 0)
        {
            //gerer parenthese et autre terme generaux + gerer ^apres: 2^2
            $final .= $equa{$i}."*";
        }
        elseif(is_numeric($equa{$i}) && $i > 0 && $equa{$i-1} != "^")
        {
            //gerer ^apres: 2^2
            $final .= $equa{$i}."*";
        }
        elseif($equa{$i} == "^")
        {
            continue;
        }
        elseif(is_numeric($equa{$i}) && $equa{$i-1} == "^")
        {
            continue;
        }
        else
        {
            if($equa{$i} == "x")
            {
                $final .= 1;
            }
            else
            {
                $final .= $equa{$i}; 
            }
        }
    }
    //
    //Manage multiplication add in the previous string $final
    //
    $finalMul = "";
    for($i = 0; $i < strlen($final); $i++)
    {
        if(is_numeric($final{$i}) && $final{$i+1} == "*" && is_numeric($final{$i+2}))
        {
            $finalMul .= $final{$i}*$final{$i+2};
        }
        elseif($final{$i} == "*")
        {
            continue;
        }
        elseif(is_numeric($final{$i}) && $final{$i+1} != "*" && $final{$i-1} == "*")
        {
            continue;
        }
        else
        {
            $finalMul .= $final{$i};    
        }
    }
    echo "equa final: ".$finalMul;
}
?>

I know this is not optimal but i've done this quick :)
If you guys have any comment just email me.
I also want to do this fonction In C to add to phpCore maybe soon...
Patoff

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daniel at g-loc dot org ¶

19 years ago

If you're an aviator and needs to calculate windcorrection angles and groundspeed (e.g. during flightplanning) this can be very useful.



$windcorrection = rad2deg(asin((($windspeed * (sin(deg2rad($tt - ($winddirection-180))))/$tas))));

$groundspeed = $tas*cos(deg2rad($windcorrection)) + $windspeed*cos(deg2rad($tt-($winddirection-180)));



You can probably write these lines more beautiful, but they work!

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lummox ¶

16 years ago

Wouldn't the following function do the same but a lot easier than the one in the comment before?

function trimInteger($targetNumber,$newLength) {
    return $targetNumber%pow(10,$newLength); 
}

down

info at gavinvincent dot co dot uk ¶

20 years ago

If you need to deal with polar co-ordinates for somereason you will need to convert to and from x,y for input and output in most situations: here are some functions to convert cartesian to polar and polar to cartesian
<?
//returns array of r, theta in the range of 0-2*pi (in radians)
function rect2polar($x,$y)
{
     if(is_numeric($x)&&is_numeric($y))
    {
        $r=sqrt(pow($x,2)+pow($y,2));
        if($x==0)
        {
             if($y>0) $theta=pi()/2;
            else $theta=3*pi()/2;
        }
        else if($x<0) $theta=atan($y/$x)+pi();
        else if($y<0) $theta=atan($y/$x)+2*pi();
        else $theta=atan($y/$x);
        $polar=array("r"=>$r,"theta"=>$theta);
        return $polar;
    }
    else return false;
}

//r must be in radians, returns array of x,y
function polar2rect($r,$theta)
{
 if(is_numeric($r)&&is_numeric($theta))
 {
        $x=$r*cos($theta);
    $y=$r*sin($theta);
    $rect=array("x"=>$x,"y"=>$y);
 }
 else
 {
   return false;
 }
}
?>

Math 函数

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