# Using sin() function

Hi, everyone !

I want to ask, when using function `sin()`, how to control it ?

I mean, when `sin()` reaches to `-1` I want to say stop and move after some time. For example, see this sketch .

I appreciate any help, thanks !

Interesting problem. The approach I would take would be to write your own function that uses sin(), but only some of the time. Like so:

``````void setup(){
size(800,400);
}

void draw(){
background(0);
stroke(255);
fill(255);
translate(0,200);
line(0,0,width,0);
noStroke();
for( int x = 0; x <width; x++){
float a = map(x,0,width,0,TWO_PI+2);
float y = sin_line(a,1);
ellipse(x,-180*y,5,5);
}

}

float sin_line(float a, float d) {
// Takes an angle a, and a line length d, and returns the sin(a), except not really.
// At the peaks of the sine curve are lines of length d where the wave stays at the peak.
while( a < 0 ){
a += TWO_PI;
}
while( a >= TWO_PI + d + d ){
a -= TWO_PI + d + d;
}
// a is now in the range 0 to TWO_PI + 2 * d.

if( a >= 0 && a < HALF_PI ){
return sin(a);
}
if( a >= HALF_PI && a < HALF_PI + d ){
return(1);
}
if( a >= HALF_PI + d && a < HALF_PI + d + PI ){
return(sin(a-d));
}
if( a >= HALF_PI + d + PI && a < HALF_PI + d + PI + d){
return(-1);
}
if( a >= HALF_PI + d + PI + d){
return(sin(a-(2*d)));
}
return(0); // Should not occur.
}
``````

If you run this, you can see that it plots a sine wave, except the wave crests are not mountain peaks, but plateaus and plains.

Yes, thank you man. This what I wanted !

Hi, sorry for disturbing, Can I achieve this effect with `cos()` function ?

cosine is just the sin() function shifted by 90° or PI/2.

``````float ofSet = 0.05;
void setup() {
size(600,400);
}

void draw() {
background(0);
fill(255,0,0);
text("Cosine",40,50);
fill(0,0,255);
text("Sine",20,350);
for(int i = 0; i < width; i++) {
stroke(255,0,0);
point(i,cos(i*ofSet)*100+height/2);
line(i,cos(i*ofSet)*100+height/2,i+1,cos( (i+1)*ofSet)*100+height/2);

stroke(0,0,255);
point(i,sin(i*ofSet)*100+height/2);
line(i,sin(i*ofSet)*100+height/2,i+1,sin( (i+1)*ofSet)*100+height/2);
}
}
``````