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/* taylor.c */
/* Jonathan P Dawson */
/* 2013-12-23 */
 
/* globals */
float pi=3.14159265359;
 
/* approximate the cosine function using Taylor series */
 
float taylor(float angle){
 
    float old, approximation, sign, power, fact;
    unsigned count, i;
 
    approximation = 1.0;
    old = 0.0;
    sign = -1.0;
    count = 1;
    power = 1.0;
    fact = 1.0;
 
    for(i=2; approximation!=old; i+=2){
        old = approximation;
 
        while(count<=i){
            power*=angle;
            fact*=count;
            count++;
        }
 
        approximation += sign*(power/fact);
        sign = -sign;
 
    }
    return approximation;
}
 
/* return the cosine of angle in radians */
 
float cos(float angle){
    return taylor(angle);
}
 
/* return the sine of angle in radians */
 
float sin(float angle){
    return cos(angle-(pi/2));
}
 
 
/* test routine */
 
void main(){
    float x;
    float step=pi/25;
 
    for(x=-2*pi; x <= 2*pi; x += step){
       file_write(x, "x");
       file_write(cos(x), "cos_x");
       file_write(sin(x), "sin_x");
    }
}