int syncrate=50;
float modulus=1000f/syncrate;
float x=0,y=0,speed=10;
float direction=0.5f;
void update(){

float distance=speed*modulus;

x=(float)(x+(distance*Math.cos(direction*Math.PI)));
y=(float)(y+(distance*Math.sin(direction*Math.PI)));
}
こんな感じ。