How to set rotation (rotate) in a circle?

Question

JavaScript

I have an earth object:

var time = new Date();
       // ctx.rotate( ((2*Math.PI)/60)*time.getSeconds() + ((2*Math.PI)/60000)*time.getMilliseconds() );
        ctx.translate(105,0);
        //ctx.fillRect(0,-12,50,24); // Shadow
        ctx.drawImage(earth,-500,-400);

There is an orbit object:

ctx.beginPath();
          ctx.arc(600,600,100,0,Math.PI*2,false); 
        ctx.stroke();

How to make the earth rotate in this orbit?

Answer 1

Sine, cosine.