Question

I’ve tried

$x = cos(deg2rad($angle));

but it returns 6.12323399574E-17 when the angle is 90 degrees instead of 0.
I read that this is a floating point problem, but is there a workaround?

Answer 1

6.1E-17 is almost zero anyway[*]. If you need to actually compare the result to zero, in floating point math you should check that it’s within a certain tolerance of the desired value, since most numbers can’t be represented correctly.

$x = cos(deg2rad($angle));
$is_zero = (abs($x) < 1e-10);

Strictly speaking, of course, zero is actually a number that can be represented correctly in floating point. The real problem is that pi / 2.0 can’t be, so the input to your cos function isn’t “correct”.

[*] To put that in context, taken as a proportion of 1 AU (the average distance from the Sun to the Earth) it is equivalent to 0.0092 millimeters, or about a tenth of the average width of a human hair…