JavaScript graphic example: Archimedes spiral

Time：2021-3-4

1. Archimedes spiral

Archimedes spiral is also known as “constant velocity spiral”. When a point P moves along the moving ray OP at the same speed, the ray rotates around the point o at the same angular speed. The trajectory of point P is called “Archimedean spiral”.

The Cartesian coordinate equation of Archimedes spiral is as follows:

r=10*(1+t)

x=r*cos(t * 360)

y=r*sin(t *360)

Write the following HTML code.

Archimedes spiral

function draw(id)

{

var canvas=document.getElementById(id);

if (canvas==null)

return false;

var context=canvas.getContext(‘2d’);

context.fillStyle=”#EEEEFF”;

context.fillRect(0,0,300,300);

context.strokeStyle=”red”;

context.lineWidth=2;

var dig=Math.PI/32;

context.beginPath();

context.moveTo(150,150);

for (var i=1;i<=256;i++)

{

x=150+5*i*dig*Math.sin(i*dig);

y=150+5*i*dig*Math.cos(i*dig);

context.lineTo(x,y);

}

context.stroke();

}

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