How to leave some things "untouched" by resetting the background

Processing Coding Questions
1

essentially what I want is for the outer line to place a dot at the tip every frame, but without the background over lapping the previous dots

static float GOLD = 1.618;

void setup() {
fullScreen(P2D);
frameRate(2000);
}

float ang1 = 0;
float ang2 = 0;
float ang3 = 0;
int s = 100;
static float e = 2.71828;

void draw() {

ang1++;
ang2++;
ang3 = ang3 + GOLD / e;

pushMatrix();
translate(width / 2, height / 2);
rotate(radians(ang1));
line(0, 0, 0, s);
popMatrix();


pushMatrix();
translate(width / 2, height / 2);
rotate(radians(ang2));
translate(0, s);
rotate(radians(ang3));
line(0, 0, 0, s);

line(0, s - 3, 0, s);
popMatrix();

}

2

I cant figure out if I can use a vector to display each dot because there’s absolutely no x or y variables other then the alignment.