Follow 3 based on code from Keith Peters.

A segmented line follows the mouse. The relative angle from each segment to the next is calculated with atan2() and the position of the next is calculated with sin() and cos().

```
float[] x = new float[20];
float[] y = new float[20];
float segLength = 18;

void setup() {
size(640, 360);
strokeWeight(9);
stroke(255, 100);
}

void draw() {
background(0);
dragSegment(0, mouseX, mouseY);
for(int i=0; i<x.length-1; i++) {
dragSegment(i+1, x[i], y[i]);
}
}

void dragSegment(int i, float xin, float yin) {
float dx = xin - x[i];
float dy = yin - y[i];
float angle = atan2(dy, dx);
x[i] = xin - cos(angle) * segLength;
y[i] = yin - sin(angle) * segLength;
segment(x[i], y[i], angle);
}

void segment(float x, float y, float a) {
pushMatrix();
translate(x, y);
rotate(a);
line(0, 0, segLength, 0);
popMatrix();
}
```

## Functions Used

stroke()

Sets the color used to draw lines and borders around shapes

size()

Defines the dimension of the display window width and height in units of pixels

pushMatrix()

Pushes the current transformation matrix onto the matrix stack

sin()

Calculates the sine of an angle

popMatrix()

Pops the current transformation matrix off the matrix stack

setup()

The setup() function is run once, when the program starts

strokeWeight()

Sets the width of the stroke used for lines, points, and the border around shapes

cos()

Calculates the cosine of an angle

rotate()

Rotates the amount specified by the angle parameter

translate()

Specifies an amount to displace objects within the display window

draw()

Called directly after setup(), the draw() function continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called

for

Controls a sequence of repetitions

atan2()

Calculates the angle (in radians) from a specified point to the coordinate origin as measured from the positive x-axis