who can understand the c of atan(); ??? pls help

[lanyong]

float const pat[4]={0.17630401, 5.6710795, 22.376096, 19.818457};
float const qat[4]={1.0000000, 11.368190, 28.982246, 19.818457};




float atan(float x)
{
float y,res,r;
int s,flag;
s=0; flag=0; y=x;
if (x < 0) { s=1; y=-y;}
if (y > 1.0) { y=1.0/y; flag=1; }
res = pat[0]*y*y + pat[1];
res = res*y*y + pat[2];
res = res*y*y + pat[3];
r = qat[0]*y*y + qat[1];
r = r*y*y + qat[2];
r = r*y*y + qat[3];
res = y*res/r;
if (flag) res = 1.57079633 - res; // for |x| > 1
if (s) res = -res;
return(res);
}
_________________
Lan Yong

[troky]

It is based on Taylor series polynomial approximation... pure math.


Troky

[lanyong]

[rwyoung]

http://www.sosmath.com/calculus/tayser/tayser01/tayser01.html

And Google will generate as many more as you care to see...

Also if you have a university near by, a trip to their math & science library will bury you in Taylor Series information.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

[lanyong]

[rwyoung]

A classic case of "use it or loose it"!

When I think back on all the Calculus, Differential Equations, Matrix & Linear Algebra, and Statistics classes I had to take and then reflect on what I use daily it makes me sad. I could have spent those years drinking and chasing women in the college bars like the business majors!
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

[lanyong]