That would be a bad idea because it would lead to discontinuities. The function should be smooth at pi/2, pi, etc. - Gordon
________________________________ From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Guido Sent: Monday, September 17, 2007 1:46 PM To: flexcoders@yahoogroups.com Subject: Re: [flexcoders] Math.cos...? Math.cos() (and every other trig function) should check the argument being PI (or any other of its own constants) before calculating, since it would better reflect the mathematical function and maybe even save up on some performance. On 9/17/07, Gordon Smith <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > wrote: In addition to Math.PI not being able to store the exact value of pi, the computation of trig functions involves approximations. For example, one definition of a cosine is in terms of an infinite series, and a computer can't calculate an infinite number of terms. Even if the argument passed to Math.cos() is exact, the result generally won't be. - Gordon ________________________________ From: flexcoders@yahoogroups.com [mailto:flexcoders@yahoogroups.com <http://yahoogroups.com> ] On Behalf Of Jon Bradley Sent: Sunday, September 16, 2007 2:49 PM To: flexcoders@yahoogroups.com Subject: Re: [flexcoders] Math.cos...? That's pretty much it. To a computer Math.cos(Math.PI/2) is not 0. It's really close to 0, because PI is an infinite sequence and a computer can "only" store it as a double precision floating point number (ie, a fixed value). What you get back from this calculation is the error bound of the computer basically, which you can then use for numerical calculations, ie, MathLib.ERROR_BOUND = Math.cos(Math.PI/2). Then you can feasibly use if you need numerical accuracy. IE, if result == MathLib.ERROR_BOUND, result = 0. Numerical accuracy in AS2 is not equivalent to that of AS3. I ran into this while porting the Mersenne Twister algorithm to AS2 - I couldn't even store 2^32 as a hex value in AS2 (0x100000000, which equals 4294967296). At least we can be somewhat numerically accurate now... good luck, jon On Sep 16, 2007, at 5:15 PM, Troy Gilbert wrote: > Why does Math.cos(Math.PI/2) not return zero? Round-off error in the Math libs? It does return a value very close to 0 (1.7xe-17). Troy.
