Math.cos not accurate! Help!

[olias32]

Hi everyone

I have the following issue which is driving me nuts.
I've written these 2 functions for returning the end coordinates of a line, when you know the starting coordinates, angle and length.

So, x1 and y1 are the starting point's coordinates, u = angle and l = length.

function degToRad(u) {
	return((u*Math.PI)/180);
}

function angleLineX(x1, y1, l, u) {
	u = degToRad(u);
	x2 = l*Math.cos(u);
	x2 = x1 + x2;
	return(x2);
}
function angleLineY(x1, y1, l, u) {
	u = degToRad(u);
	y2 = l*Math.sin(u);
	y2 = y1 - y2;
	return(y2);
}

The degToRad() function just converts the angle from degrees to radians.
These functions usually work pretty well, but i came across a few values which don't seem to work.

a = angleLineX(0, 0, 864, 89.67);
b = angleLineX(0, 0, 864, 89.66);
trace(a + " - " + b);

the output to the above is

0.69 - 9.33

If i change it to

a = angleLineX(0, 0, 864, 89.68);
b = angleLineX(0, 0, 864, 89.67);
trace(a + " - " + b);

the output becomes

0.69 - 0.69

So, if i change the angle by 0.01 degrees i get the huge difference in the x coordinate, but only from 89.66 to 89.67
Otherwise, from 89.67 to 89.68 there's virtually no change

Can someone please help me?
Am i doing something wrong? I'm guessing the cos function is not very accurate, as you can see from the help file

Note: The cosine of a 90 degree angle is zero, but because of the inherent inaccuracy of decimal calculations using binary numbers, Flash Player will report a number extremely close to, but not exactly equal to, zero.

Not very accurate, ok, but to that extent?
Also, can anyone sugesst a fix or alternative to doing that?

Thanks

[olias32]

fixed. thanks

It wasn't a problem with the cos function but with a Math.round i was using when converting from degrees to radians,
which i forgot about.