Bird - 2013-01-26

I want to make the program about Physics:
initial value: x(0),y(0),vx(0),vy(0)
I can find r(0)=x(0)+y(0),ax(0)=x(0)/r(0),ay(0)=y(0)/r(0)
Then,I find vx(t/2)=vx(0)+ax(0)t,vy(t/2)=vy(0)+ay(0)t
Therefore,I can calculate x(t)=x(0)+vx(t/2)t,y(t)=y(0)+vy(t/2)t
then, r(t)=x(t)+y(t),ax(t)=x(t)/r(t),ay(t)=y(t)/r(t)
It's only vx(t/2),vy(t/2) have different calculation methods,
but other's will cycle like this:0→t,t→2t,2t→3t;
vx(3t/2),vy(3t/2) will cycle: 3t/2→5t/2,5t/2→7t/2,7t/2→9t/2.
I want Dev C++ print all x(t),y(t) until t<T.
However,the relation between x,y,r,vx,vy,ax,ay makes me crazy.
I have tried many many hours, and I hope someone can help me.
I will very grateful to you!