[Resolved] The math thread

[Merve]

Hello, this is the place if you need help on basic math in PHP. And so do I! I'm a newbie. So yeah, can anybody help me with sine cosine and tangent. Using sin() cos() and tan() doesn't seem to work for me.
I eventually want to make a multi-function calculator that can do a lot of stuff. So far, it can't do very much. You can view it at vv.carleton.ca/~adewan/calculator.html and it's really easy to use.
Oh yeah, just to tell you guys messing around with 'pi' don't do it! Use M_PI because it's so much more powerful. pi doesn't seem to work in mathematical equations (maybe that's because I'm a doofus). Anyway, have fun.

[Merve]

forget about helping me with sin() cos() and tan() i figured out what i was doing wrong

[Merve]

it seems to work with sin() but not with cos() or tan() somebody please help me

[stolzyboy]

why don't you give us an example of what you are using when it doesn't work so we can check it out

[Weedpacket]

I have to say that this is one of the sillier polls I've ever seen 🙂

[stolzyboy]

yeah i thought it was kinda crazy too

which is better, i mean, come on, you will essentially and eventually need all of them

[Merve]

Yup, you guys are right. They're all equally important. It just depends on what you want to do. So far I've found * the most useful but + and - have come in really handy. % is pretty cool and so is / so what's the point in the end of debating? But I know people who argue that multiplication and division are just looped addition and subtraction (how dumb and non-lazy they are!). So here's a little bit of my coding. Basically, there are two one-line text fields you have to fill in, and a pulldown menu. You select the operation you want, and you get the correct answer (usually). I tried to use sine, cosine and tangent, but I can't get them to work. Is the default setting radians, degrees, or grads, or am I just stupid?
I mean...
<?php
$c = sin($b);
print (" The sine of $b is $c");
?>
Assuming $b is equal to 90, this should give 1, right? But I get something weird like 0.89399666360056 and that just sort of makes me wonder what's going on. I'm getting even weirder results with cosine and tangent. Please help the newbie weirdo!
You can see the calculator in action at vv.carleton.ca/~adewan/calculator.html

[paulnaj]

Most trig functions in programming languages/scripting languages use radians not degrees.

Here's a function to convert degrees to radians ...

function deg_to_rad($degrees){
    return $degrees * M_PI/180;
}

So, if you are used to working in degrees, carry on doing so, but when you need to calculate a trig function, use the above to convert the degrees variable to a radians variable before passing it to the trig function.

[Merve]

It seems to work with sine but not with cosine or tangent. I am confused. Thanks for the function.

[ScubaKing22]

I voted / because no one else did...poor little fella felt left out 🙁

[Merve]

Here's some stuff if you ever need it, although I'm sure you could have figured it out on your own.

Square roots:

<?php
if ($b<0) {
$c = sqrt($b*-1);
print (" The square root of $b &#61; &plusmn;$c<i>i</i>");
} else {
$c = sqrt($b);
print (" The square root of $b &#61; $c");
}
?>

This square root tool can do the square roots of negative numbers as well.

Factorials:

<?php
$e = intval($a);
if ($a!=$e) {
print (" You must fill in an integer greater than -1.");
}
elseif ($a<0) {
print (" You must fill in an integer greater than -1."); 
}
elseif ($a==0) {
print (" $a! = 1");
} else {
$c = ($a-1);
$d = $a;
while ($c>=1)
{
$a = ($a*$c);
$c--;
}
print (" $d! = $a");
}
?>

With this, people have to fill in an integer greater than -1. It really is simple to check if people are using decimal numbers. Instead of intval(), you can use round(), ceil(), or floor(). They should (I think) yield the same results.

Division with remainder:

<?php
elseif ($operation=="div2") {
$c = (intval ($a/$b));
$d = ($a%$b);
print (" $a &divide; $b &#61; $c R $d");
}
?>

You can check out the calculator at vv.carleton.ca/~adewan/calculator.html.

Oh yeah, I'm STILL having trouble with sin() cos() and tan(). Please help me. I need to change radians into degrees without actually changing the value (e.g. 90 radians becomes 90 degrees). Can anybody please help me?

Oh yeah, smilies kind of suck.

The end...I think

[paulnaj]

Show us what trouble you are having ...

Here's a test that shows sin, cos and tan all working , run it ...

function deg_to_rad($degrees){ return $degrees * M_PI/180; }
echo "<table border=\"1\" cellspacing=\"2\" cellpadding=\"2\">\n";
echo "<tr><th>Degrees</th><th>Radians</th><th>cos(radians)</th><th>sin(radians)</th><th>tan(radians)</th></tr>\n";
for($i = 0; $i < 24; $i++){
	$d = 15*$i;
	$r = deg_to_rad($d);
	echo "<tr><td>".$d."</td><td>".$r."</td><td>".cos($r)."</td><td>".sin($r)."</td><td>".tan($r)."</td></tr>\n";
}
echo "</table>\n";

[Merve]

Here's what I've got so far...

<?php
if ($operation=="plus") {
$c = ($a+$b);
print (" $a &#43; $b &#61; $c");
}
elseif ($operation=="minus") {
$c = ($a-$b);
print (" $a - $b &#61; $c");
}
elseif ($operation=="times") {
$c = ($a*$b) ;
print (" $a &times; $b &#61; $c");
}
elseif ($operation=="divided") {
$c = ($a/$b);
print (" $a &divide; $b &#61; $c");
}
elseif ($operation=="div2") {
$c = (intval ($a/$b));
$d = ($a%$b);
print (" $a &divide; $b &#61; $c R $d");
}
elseif ($operation=="power") {
$c = pow($a, $b);
print (" $a<sup>$b</sup> &#61; $c");
}
elseif ($operation=="sqrt") {
if ($b<0) {
$c = sqrt($b*-1);
print (" The square root of $b &#61; &plusmn;$c<i>i</i>");
} else {
$c = sqrt($b);
print (" The square root of $b &#61; $c");
}
}
elseif ($operation=="factorial") {
$e = intval($a);
if ($a!=$e) {
print (" You must fill in an integer greater than -1.");
}
elseif ($a<0) {
print (" You must fill in an integer greater than -1."); 
}
elseif ($a==0) {
print (" $a! = 1");
} else {
$c = ($a-1);
$d = $a;
while ($c>=1)
{
$a = ($a*$c);
$c--;
}
print (" $d! = $a");
}
}
elseif ($operation=="percentage") {
$c = (($a/100)*($b));
print (" $a&#37; of $b &#61; $c");
}
elseif ($operation=="rebate") {
$c = (($b)-(($a/100)*($b)));
print (" A/an $a&#37; rebate on $b would give $c");
}
elseif ($operation=="tax") {
$c = (($b)+(($a/100)*($b)));
print (" A/an $a&#37; tax on $b would give $c");
}
elseif ($operation=="hypotenuse") {
if ($b<=0) {
print (" Lengths must be greater than 0.");
} 
elseif ($a<=0) {
print (" Lengths must be greater than 0.");
} else {
$c = sqrt(($a*$a)+($b*$b));
print (" If the sides of a right triangle forming the right angle are $a and $b respectively, then the hypotenuse would be $c.");
}
}
elseif ($operation=="misside") {
if ($a<=$b) {
print (" The hypotenuse in a right-angled triangle is the longest side!");
}
elseif ($b<=0) {
print (" Lengths must be greater than 0.");
}
elseif ($a<=0) {
print (" Lengths must be greater than 0.");
} else {
$c = sqrt(($a*$a)-($b*$b));
print (" If the hypotenuse of right triangle is $a and another side is $b, then the missing side would be $c.");
}
}
elseif ($operation=="circumference") {
if ($a<=0) {
print (" Lengths must be greater than 0.");
} else {
$diameter = ($a/M_PI);
$diameter2 = round ($diameter, 4);
$radius = ($diameter/2);
$radius2 = round ($radius, 4);
$area = ((M_PI)*($radius*$radius));
$area2 = round ($area, 4);
print (" If the circumference of a circle is $a unit(s), then the diameter is $diameter2 unit(s), the radius is $radius2 unit(s), and the area is $area2 square unit(s).");
}
}
elseif ($operation=="diameter") {
if ($a<=0) {
print (" Lengths must be greater than 0.");
} else {
$circumference = ($a*M_PI);
$circumference2 = round ($circumference, 4);
$radius = ($a/2);
$radius2 = round ($radius, 4);
$area = ((M_PI)*($radius*$radius));
$area2 = round ($area, 4);
print (" If the diameter of a circle is $a unit(s), then the circumference is $circumference2 unit(s), the radius is $radius2 unit(s), and the area is $area2 square unit(s).");
}
}
elseif ($operation=="radius") {
if ($a<=0) {
print (" Lenghts must be greater than 0.");
} else {
$diameter = ($a*2);
$diameter2 = round ($diameter, 4);
$circumference = ($diameter*M_PI);
$circumference2 = round ($circumference, 4);
$area = ((M_PI)*($a*$a));
$area2 = round ($area, 4);
print (" If the radius of a circle is $a unit(s), then the circumference is $circumference2 unit(s), the diameter is $diameter2 unit(s), and the area is $area2 square unit(s).");
}
}
elseif ($operation=="area") {
if ($a<=0) {
print (" Lengths must be greater than 0.");
} else {
$radius = sqrt($a/M_PI);
$radius2 = round ($radius, 4);
$diameter = ($radius*2);
$diameter2 = round ($diameter, 4);
$circumference = ($diameter*M_PI);
$circumference2 = round ($circumference, 4);
print (" If the area of a circle is $a square unit(s), then the circumference is $circumference2 unit(s), the diameter is $diameter2 unit(s), and the radius is $radius2 unit(s).");
}
}
elseif ($operation=="sine") {
$c = rad2deg($b);
$d = $b*M_PI/180;
$e = sin($d);
print (" The sine of $b is $e.");
}
elseif ($operation=="cosine") {
$c = rad2deg($b);
$d = $b*M_PI/180;
$e = cos($d);
print (" The cosine of $b is $e.");
}
elseif ($operation=="tangent") {
$c = rad2deg($b);
$d = $b*M_PI/180;
$e = tan($d);
print (" The tangent of $b is $e.");
}
?>

I don't know why the sines, cosines and tangents aren't working. Please help me!
I hope to add logarithmic functions to this calculator.
You can view it here.
Please help the newbie!

Oh yeah, if you ever need help, I'll try, and so will everybody, so you can post your problems here insteading of always looking at my rants and raves about how my trignometric functions won't work.

[Weedpacket]

Love to, but I don't see them misbehaving at all (incidentally, you never actually use $c for the trig functions, and hence never use rad2deg() either). Do you have a few examples? Is it a matter of precision (due to the limitations of floating-point arithmetic, cos(90&deg😉 is not quite equal to 0?

[Merve]

You see, the problem is, it seems to work for sine, but not for cosine or tangent, but the sine of 90 degrees is exactly 1. I looked at the curves.

If anybody has problems please ask and I and other people who regulary visit this thread will be glad to help (or in my case attempt to help).

[Merve]

Thank you very much, paulnaj. Even though you gave the answers in radians, it really helped me figure out what was going wrong with my calculations. It was so simple; it was right in front of my nose the whole time; I'll see if it works now, thank you.

[Merve]

I want to know if there's anything else I should add to my calculator.

It can add, subtract, multiply, divide, divide with remainder, do square roots, do powers, do factorials, use the pythagorean theorem, can calculate the area, circumference, diameter and radius of a circle knowing only one of those values, can do logs, natural logs, e to the power of x, and some trignometric functions.
Or at least, it can do most of it. I'm not done yet. I'm thinking of adding something that can convert degrees, radians and grads. I don't think hyperbolic functions will be very useful (because I don't understand what they are, I mean, I'm not that advanced in math. I know around grade 10 math, so I don't see the point of messing around with things I don't know.

If there's anything, anything at all I should add, please tell me, and don't tell me to add hyperbolic functions because I won't do it.

I may make a separate probability calculator, but I don't think that will happen in the near future. (calculates Omega, the cardinal, etc.)

Thanks to everybody for your help.

If you need any help, just post your problem here, and I'll continue with updates on the calculator, which you can view at this page.

I'm happy to help!

[Merve]

I'm marking this thread resolved

[pjleonhardt]

you should add a graphing calculator on to it 😃

[LordShryku]

Digging through the old threads and found this gem, eh?